DOCSLIB.ORG

Role of Wild Type P53 in the G2 Phase: Regulation of the G-Irradiation- Induced Delay and DNA Repair

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Role of Wild Type P53 in the G2 Phase: Regulation of the G-Irradiation- Induced Delay and DNA Repair Oncogene (1997) 15, 2597 ± 2607 1997 Stockton Press All rights reserved 0950 ± 9232/97 $12.00 Role of wild type p53 in the G2 phase: regulation of the g-irradiation- induced delay and DNA repair Dov Schwartz, Nava Almog, Amnon Peled, Naomi Gold®nger and Varda Rotter Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel 76100 Upregulation of the p53 protein was shown to induce cell al., 1995; Wells, 1996). We have recently found that cycle arrest at the G1/S border and in some cases at the both the loss of wild type p53, or overexpression of G2/M border. Furthermore, it was suggested that p53 is mutant p53 in myeloid cells, are associated with associated with the induction of the various DNA repair polyploidity (Peled et al., 1996). This supports the pathways. Previously, we demonstrated that cells co- conclusion that p53 may play a role at the spindle expressing endogenous wild type p53 protein, together checkpoint. with dominant negative mutant p53, exhibit deregulation p53 was shown to be involved in active cellular of apoptosis, G1 arrest and delay in G2 following g- repsonses that remove DNA damage, either by repair irradiation. In the present study, we investigated the role of the damaged DNA, or by an active killing of p53 protein in the DNA damage response at the G2 (apoptosis) of cells possessing extensive, unrepairable phase. Using p53-null, wild type p53 and mutant p53- DNA damage (reviewed in Enoch and Norbury, 1995). producer cell lines, we found that the two C-terminally p53-dependent apoptosis is triggered by various stress spliced p53 forms could prevent g-irradiation induced conditions, resulting in a clastrogenic eect on the mutagenesis prior to mitosis, at the G2/M checkpoint. DNA (Yonish-Rouach et al., 1991, 1993; Lowe and We found that at the G2 phase, p53 may facilitate repair Ruley, 1993; Lowe et al., 1993; Lee et al., 1993; Clarke of DNA breaks giving rise to micronuclei, and regulate et al., 1993; Symonds et al., 1994). The activity of p53 the exit from the G2 checkpoint. At the G1 phase, only in DNA repair processes (Pan et al., 1995; Wang et al., the regularly spliced form of p53 caused growth arrest. 1995, 1996; Ford and Hanawalt, 1995; Bogue et al., In contrast, both the regularly and the alternatively 1996; McDonald III et al., 1996) was shown to be spliced p53 forms directed postmitotic micronucleated controlled by the C-terminus of the molecule, that cells towards apoptosis. These results provide a func- binds several DNA repair-related proteins, including tional explanation for the cell cycle-independent expres- the human Rad51 (Sturzbecher et al., 1996), RPA sion of p53 in normal cycling cells, as well as in cells (Dutta et al., 1993) and ERCC3 (Wang et al., 1994, where p53 is up-regulated, following DNA damage. 1995). In addition, GADD45 and the waf-1 gene, that are transcriptionally regulated by p53, were found to Keywords: p53; G2 checkpoint; DNA damage; micro- bind PCNA, another DNA repair protein (Chen et al., nucleated cells 1995). Moreover, the last 100 amino acids of human p53 contain non-speci®c single strand (Bakalkin et al., 1994, 1995; Jayaraman and Drives, 1995) and mismatched (Lee, et al., 1995) DNA binding activity. Introduction The C-terminal domain of the regularly spliced p53 form (RSp53), also contains a DNA helicase activity It is well established that p53 is up regulated by various (Brain and Jenkins, 1994; Bakalkin et al., 1995; Wu et stress conditions, characterized by DNA damage al., 1995), characteristic of many DNA repair proteins. induction (Maltzman, Czyzyc, 1984; Fritsche et al., The eect of p53 on DNA repair is also evident 1993; Nelson and Kastan, 1994). One of the major from measuring residual DNA damage following proposed functions for p53 under these conditions, is genotoxic stress. One of the detectable manifestations the maintenance of genomic stability (Livingstone et of residual DNA damage in cells following g- al., 1992; Lane, 1992; Yin et al., 1992; Symonds et al., irradiation is the appearance of micronuclei (Heddle, 1994). Carrano, 1977). Micronuclei originate from acentric p53 was suggested to play a role in growth arrest at double strand breaks in chromosomes and from the G1/S border prior to DNA replication, and at the dicentric chromosomes, that give rise to chunks of G2 phase prior to mitosis, by allowing the repair of chromatin that do not segregate with the rest of the faulty DNA that accumulates in cells (Kastan et al., genome after mitosis, but are often separately engulfed 1991, 1992; Di Lionardo et al., 1994). p53 was also by the nuclear membrane (Heddle and Carrano, 1977; shown to regulate the spindle checkpoint in mitotic Nusse et al., 1994). Thus, the presence of micronuclei embryonic ®broblasts. This checkpoint prevents the in cells is an indicator of either chromosomal formation of aneuploid cells that are bound to harbor aberrations that were not repaired until completion of an unstable genome after cytokinesis, and also prevents mitosis, or of an unstable karyotype. Interestingly, ectopic DNA endoreduplication in these cells (Cross et reticulocytes from p53-knockout mice contain elevated levels of micronuclei under normal growth conditions and in cells with DNA damage (Lee et al., 1994). Moreover, bone marrow cells from these mice exhibit a Correspondence: V Rotter high frequency of chromosomal abnormalities (Bouer Received 29 April 1997; revised 18 July 1997; accepted 21 July 1997 et al., 1995). Furthermore, wild type p53, in contrast to p53 and the G2 checkpoint D Schwartz et al 2598 mutant p53, was found to accumulate in micronuclei of cells that are p53-null lymphoid pre-B, stably g-irradiated hepatoma cell lines (Unger et al., 1994). expressing regularly (RSp53) or alternatively-spliced Although it is clear that the onset of the G2 p53 (ASp53) forms and their mutant counterparts, checkpoint is p53-independent, and involves a rapid were analysed. Both alternatively spliced wild type p53 phosphorylation of the MPF cyclin B1-cdc2 complex, forms facilitated the exit from the g-irradiation- p53 may play a role as a secondary regulator of the G2 dependent G2 delay. Analysis of micronuclei content delay (Stewart et al., 1994; Paules et al., 1995). In following exit from the G2 delay indicated that cell several p53-null non-lymphoid cell lines, reconstitution lines expressing the two forms of wild type p53 of wild type p53 conformation (Stewart et al., 1994), or exhibited 20% of micronuclei detected in p53-null transcriptional induction of wild type p53 without any cells. Analysis of p53 distribution in post mitotic DNA damage (Agarwal et al., 1995) resulted in a G2- diploid micronucleated cells indicated that wild type as well as a G1- arrest. The role of p53 as a second p53 accumulates in the L12 cells expressing wild type barrier at the G2 checkpoint, is further supported by p53, and promotes their apoptosis. This eect was not the ®nding that annihilation of the phosphorylation- related to the spindle checkpoint, since in these cells dependent G2-delay by caeine, is reduced in wild type this checkpoint was p53-independent. While both p53 expressing cells (Powell et al., 1995). This agrees alternatively spliced p53 forms are involved in the with our observation that functional inactivation of G2-related activities, the ability to arrest at the G1/S endogenous p53 in lymphoid cells, by stably expressing border following g-irradiation was evident only in L12 dominant negative mutant p53, induces premature exit cells reconstituted with wild type RSp53. from the g-irradiation-dependent G2 arrest (Aloni- Grinstein et al., 1995). The goal of this study was to elucidate the role of Results p53 in the response to DNA damage at the G2 phase. We compared the time course of the cell cycle, the Wild type p53 controls the kinetics of exit from G delay repair of DNA damage following g-irradiation of cells 2 in g-irradiated L12 cells at the G2 phase and the selective apoptosis of micronucleated postmitotic cells. Since most of the Previous data indicated that wild type p53 plays a role DNA repair associated activites were ascribed to the in the G2 checkpoint. To analyse this activity, regularly spliced C-terminal of p53 (Shaulian et al., logarithmically growing cells of p53 producer and 1994; Lee et al., 1995; Wu et al., 1995), we compared non-producer L12 derivatives were enriched for the eect of re-introduction into p53 null cells of the tetraploid DNA constant by centrifugal elutriation two alternatively spliced p53 forms that vary at their under viable conditions. The cells were collected, C-terminal (Wolf et al., 1985; Arai et al., 1986). L12 replated and g-irradiated (with 300 R), or kept under Figure 1 Wild type p53 accelerates the exit from the G2 delay after irradiation: Cell cycle patterns. L12 clones expressing regular spliced wild type RSp53-10 (marked in gray in a, b, c, alternatively spliced wild type ASp53-22 (marked as empty in a, b, c)or empty pSVL plasmid, clone pSVL-3 (marked in black in a, b, c) were grown at logarithmic conditions and enriched for the G2 phase using centrifugal elutriation under viable conditions (a). Normal cell cycle distribution is depicted by dotted line in a. The cells were either directly replated, or g-irradiated (300 R) and then replated. (b) shows the cell cycle of pattern g-irradiated cells 12 h after g- irradiation. (c) shows the cell cycle pattern of non-irradiated clones, 6 h after replating. (d, e, f) parallel (a, b, c) except that the clones used in these experiments are mutant RSp53-M11-3 (marked in gray), mutant ASp53-M8-3A2 (marked as empty) or empty pSVL plasmid pSVL-3 (marked in black) p53andtheG2 checkpoint D Schwartz et al 2599 the same conditions as the g-irradiated cells, and as the G2-enriched fractions.
Load more

Recommended publications
  • Mitosis Vs. Meiosis
    Mitosis vs. Meiosis In order for organisms to continue growing and/or replace cells that are dead or beyond repair, cells must replicate, or make identical copies of themselves. In order to do this and maintain the proper number of chromosomes, the cells of eukaryotes must undergo mitosis to divide up their DNA. The dividing of the DNA ensures that both the “old” cell (parent cell) and the “new” cells (daughter cells) have the same genetic makeup and both will be diploid, or containing the same number of chromosomes as the parent cell. For reproduction of an organism to occur, the original parent cell will undergo Meiosis to create 4 new daughter cells with a slightly different genetic makeup in order to ensure genetic diversity when fertilization occurs. The four daughter cells will be haploid, or containing half the number of chromosomes as the parent cell. The difference between the two processes is that mitosis occurs in non-reproductive cells, or somatic cells, and meiosis occurs in the cells that participate in sexual reproduction, or germ cells. The Somatic Cell Cycle (Mitosis) The somatic cell cycle consists of 3 phases: interphase, m phase, and cytokinesis. 1. Interphase: Interphase is considered the non-dividing phase of the cell cycle. It is not a part of the actual process of mitosis, but it readies the cell for mitosis. It is made up of 3 sub-phases: • G1 Phase: In G1, the cell is growing. In most organisms, the majority of the cell’s life span is spent in G1. • S Phase: In each human somatic cell, there are 23 pairs of chromosomes; one chromosome comes from the mother and one comes from the father.
    [Show full text]
  • Targeting the WEE1 Kinase As a Molecular Targeted Therapy for Gastric Cancer
    www.impactjournals.com/oncotarget/ Oncotarget, Vol. 7, No. 31 Research Paper Targeting the WEE1 kinase as a molecular targeted therapy for gastric cancer Hye-Young Kim1,2, Yunhee Cho1,3, HyeokGu Kang1,3, Ye-Seal Yim1,3, Seok-Jun Kim1,3, Jaewhan Song2, Kyung-Hee Chun1,3 1Department of Biochemistry & Molecular Biology, Yonsei University College of Medicine, Seodaemun-gu, Seoul 03722, Korea 2Department of Biochemistry, College of Life Science and Biotechnology, Seodaemun-gu, Seoul 03722, Korea 3Brain Korea 21 PlusProject for Medical Science, Yonsei University, Seodaemun-gu, Seoul 03722, Korea Correspondence to: Kyung-Hee Chun, email: [email protected] Keywords: WEE1, AZD1775 (MK-1775), 5-FU, Paclitaxel, gastric cancer Received: September 07, 2015 Accepted: May 28, 2016 Published: June 23, 2016 ABSTRACT Wee1 is a member of the Serine/Threonine protein kinase family and is a key regulator of cell cycle progression. It has been known that WEE1 is highly expressed and has oncogenic functions in various cancers, but it is not yet studied in gastric cancers. In this study, we investigated the oncogenic role and therapeutic potency of targeting WEE1 in gastric cancer. At first, higher expression levels of WEE1 with lower survival probability were determined in stage 4 gastric cancer patients or male patients with accompanied lymph node metastasis. To determine the function of WEE1 in gastric cancer cells, we determined that WEE1 ablation decreased the proliferation, migration, and invasion, while overexpression of WEE1 increased these effects in gastric cancer cells. We also validated the clinical application of WEE1 targeting by a small molecule, AZD1775 (MK-1775), which is a WEE1 specific inhibitor undergoing clinical trials.
    [Show full text]
  • The Cell Cycle & Mitosis
    The Cell Cycle & Mitosis Cell Growth The Cell Cycle is G1 phase ___________________________________ _______________________________ During the Cell Cycle, a cell ___________________________________ ___________________________________ Anaphase Cell Division ___________________________________ Mitosis M phase M ___________________________________ S phase replication DNA Interphase Interphase is ___________________________ ___________________________________ G2 phase Interphase is divided into three phases: ___, ___, & ___ G1 Phase S Phase G2 Phase The G1 phase is a period of The S phase replicates During the G2 phase, many of activity in which cells _______ ________________and the organelles and molecules ____________________ synthesizes _______ molecules. required for ____________ __________ Cells will When DNA replication is ___________________ _______________ and completed, _____________ When G2 is completed, the cell is synthesize new ___________ ____________________ ready to enter the ____________________ ____________________ ____________________ ____________________ ____________________ Mitosis are divided into four phases: _____________, ______________, _____________, & _____________ Below are cells in two different phases of the cell cycle, fill in the blanks using the word bank: Chromatin Nuclear Envelope Chromosome Sister Chromatids Nucleolus Spinder Fiber Centrosome Centrioles 5.._________ 1.__________ v 6..__________ 2.__________ 7.__________ 3.__________ 8..__________ 4.__________ v The Cell Cycle & Mitosis Microscope Lab:
    [Show full text]
  • The Cell Cycle Coloring Worksheet
    Name: Date: Period: The Cell Cycle Coloring Worksheet Label the diagram below with the following labels: Anaphase Interphase Mitosis Cell division (M Phase) Interphase Prophase Cytokinesis Interphase S-DNA replication G1 – cell grows Metaphase Telophase G2 – prepares for mitosis Then on the diagram, lightly color the G1 phase BLUE, the S phase YELLOW, the G2 phase RED, and the stages of mitosis ORANGE. Color the arrows indicating all of the interphases in GREEN. Color the part of the arrow indicating mitosis PURPLE and the part of the arrow indicating cytokinesis YELLOW. M-PHASE YELLOW: GREEN: CYTOKINESIS INTERPHASE PURPLE: TELOPHASE MITOSIS ANAPHASE ORANGE METAPHASE BLUE: G1: GROWS PROPHASE PURPLE MITOSIS RED:G2: PREPARES GREEN: FOR MITOSIS INTERPHASE YELLOW: S PHASE: DNA REPLICATION GREEN: INTERPHASE Use the diagram and your notes to answer the following questions. 1. What is a series of events that cells go through as they grow and divide? CELL CYCLE 2. What is the longest stage of the cell cycle called? INTERPHASE 3. During what stage does the G1, S, and G2 phases happen? INTERPHASE 4. During what phase of the cell cycle does mitosis and cytokinesis occur? M-PHASE 5. During what phase of the cell cycle does cell division occur? MITOSIS 6. During what phase of the cell cycle is DNA replicated? S-PHASE 7. During what phase of the cell cycle does the cell grow? G1,G2 8. During what phase of the cell cycle does the cell prepare for mitosis? G2 9. How many stages are there in mitosis? 4 10. Put the following stages of mitosis in order: anaphase, prophase, metaphase, and telophase.
    [Show full text]
  • Absence of a Measurable G2 Phase in Two Chinese Hamster Cell Lines (Cell Cycle/V79 Cells/Autoradiography) R
    Proc. Natl. Acad. Sci. USA Vol. 74, No. 4, pp. 1622-1625, April 1977 Cell Biology Absence of a measurable G2 phase in two Chinese hamster cell lines (cell cycle/V79 cells/autoradiography) R. MICHAEL LISKAY Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309 Communicated by David M. Prescott, January 28, 1977 ABSTRACT Evidence is resented that demonstrates the been dipped in H20 and either air- or flame-dried. The slides absence of a measurable G2 prase in the cell cycles of two sub- were coated with NTB2 emulsion, dried, exposed for 7-28 days, lines of the Chinese hamster lung fibroblast V79. One of the sublines, in addition, lacks a detectable G1 phase, thereby pos- developed, and stained with crystal violet or Giemsa. The slides sessing a cell cycle comprised of simply two phases, DNA syn- were then scored for % labeled nuclei and % labeled meta- thesis (S) and mitosis (M). phases. An estimation of the length of the mitotic stages in V79-8 was The cell life cycle of most mammalian cells can be described obtained by examining living cells as they grew at 370 in flasks in terms of four phases (1): mitosis (M), a period between mitosis placed on the stage of an inverted phase contrast microscope. and the initiation of DNA replication (G1), DNA replication The first visible change in nuclear morphology (i.e., nuclear (S), and a period between the termination of DNA replication condensation as evidenced by a grainy appearance of the nu- and the beginning of prophase (G2).
    [Show full text]
  • Wee1 Kinase Inhibitor AZD1775 Effectively Sensitizes Esophageal Cancer to Radiotherapy
    Author Manuscript Published OnlineFirst on March 27, 2020; DOI: 10.1158/1078-0432.CCR-19-3373 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Wee1 Kinase Inhibitor AZD1775 Effectively Sensitizes Esophageal Cancer to Radiotherapy Linlin Yang1, Changxian Shen1, Cory Pettit1, Tianyun Li1, Andrew Hu1, Eric Miller1, Junran Zhang1, Steven H. Lin2, Terence M. Williams1, * 1The Ohio State University Medical Center, Arthur G. James Comprehensive Cancer Center and Richard J. Solove Research Institute, Columbus, Ohio. 2The University of Texas MD Anderson Cancer Center, Houston, Texas. *Corresponding Author: Terence M. Williams, Department of Radiation Oncology, The Ohio State University, 460 W. 12th Avenue, BRT/Room 492, Columbus, OH 43210-1280. Phone: (614) 293-3244. Fax: 614-293-4044. E-mail: [email protected] Running title: Targeting Wee1 for radiosensitization of esophageal cancer Key words: Wee1, AZD1775, G2 checkpoint, mitotic catastrophe, esophageal cancer Conflicts of Interest: The authors report no potential conflicts of interest. Financial Disclosure Statements: All authors have no competing financial interests to disclose. Funding Support: This work was supported by the following grants: The Ohio State University Comprehensive Cancer Center (OSU-CCC), National Institutes of Health (P30 CA016058 and R01 CA198128), and National Center for Advancing Translational Sciences (KL2TR001068). 1 Downloaded from clincancerres.aacrjournals.org on September 29, 2021. © 2020 American Association for Cancer Research. Author Manuscript Published OnlineFirst on March 27, 2020; DOI: 10.1158/1078-0432.CCR-19-3373 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. ABSTRACT Purpose: Esophageal cancer (ESCA) is a deadly malignancy with a 5-year survival rate of only 5-20%, which has remained unchanged for decades.
    [Show full text]
  • Cyclin-Dependent Kinase 6 Is the Principal Target of P27ikipl Regulation of the G1-Phase Traverse in 1,25-Dihydroxyvitamin D3-Treated HL6O Cells'
    [CANCER RESEARCH57. 2851—2855.July15. 19971 Advances in Brief Cyclin-dependent Kinase 6 Is the Principal Target of p27IKipl Regulation of the G1-phase Traverse in 1,25-Dihydroxyvitamin D3-treated HL6O Cells' Qing Mei Wang, Xun Luo, and George P. Studzinski2 Department of Pathology and Laboratory Medicine, University ofMedicine and Dentistry ofNew Jersey-New Jersey Medical School, Newark, New Jersey 07103 Abstract specific increase in Cdk6-associated p27/Kipl protein in l,25D3- treated wild-type HL6O (HL6O-G) cells but not in a 1,25D3-resistant Control of cell proliferation remains of intense interest in cancer re subline of HL6O (4OAF) cells. This provides a mechanism for 1,25D3- search. In the 1,25-dihydroxyvitamin D3 HL6O cell system, G1 arrest has mediated G1 arrest in wild-type HL6O cells. been shown to be mediated by elevated levels of p27/Kipi protein. We show here that the main target of the elevated p27IKipl in this system is Materials and Methods cyclin-dependent kinase (Cdk) 6. The activity of Cdk2 is also down regulated, and this is associated with altered and reduced levels of cyclin Cell Culture. HL6O-Gcells,a subcloneof HL6Opromyelocyticleukemia E in the kinase complex. Paradoxically, the kinase activity of Cdk4 is cells, were maintained in RPMI 1640 supplemented with I% glutamine and elevated, in spite ofan almost complete G1 block. These data show that the 10% complement-inactivated bovine calf serum. The 1,25D3-resistant HL6O functions of Cdk4 and Cdk6 are not redundant and that Cdk6 and Cdk2 subline (4OAF) was derived as described (4).
    [Show full text]
  • Activity and Expression Pattern of Cyclin-Dependent Kinase 5 in the Embryonic Mouse Nervous System
    Development 119, 1029-1040 (1993) 1029 Printed in Great Britain © The Company of Biologists Limited 1993 Activity and expression pattern of cyclin-dependent kinase 5 in the embryonic mouse nervous system Li-Huei Tsai1,*, Takao Takahashi2, Verne S. Caviness Jr2 and Ed Harlow1 1Massachusetts General Hospital Cancer Center, Building 149, 13th Street, Charlestown, MA 02129, USA 2Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA *Author for correspondence SUMMARY Cyclin-dependent kinase 5 (cdk5) was originally isolated ing and fell to barely detectable levels at E17 at the end on the basis of its close primary sequence homology to of the cytogenetic period. Immunohistochemical studies the human cdc2 serine/threonine kinase, the prototype showed that cdk5 is expressed in postmitotic neurons but of the cyclin-dependent kinases. While kinase activities not in glial cells or mitotically active cells. Expression of of both cdc2 and cdk2 are detected in proliferating cells cdk5 was concentrated in fasciculated axons of postmi- and are essential for cells to progress through the key totic neurons. In contrast to other cell division cycle transition points of the cell cycle, cdk5 kinase activity has kinases to which it is closely related, cdk5 appears not to been observed only in lysates of adult brain. In this be expressed in dividing cells in the developing brain. study, we compared the activity and expression of cdk5 These observations suggest that cdk5 may have a role in with that of cdc2 and cdk2 in the embryonic mouse neuronal differentiation but not in the cell division cycle forebrain.
    [Show full text]
  • Downregulation of Cell Cycle and Checkpoint Genes by Class I HDAC Inhibitors Limits Synergism with G2/M Checkpoint Inhibitor MK-1775 in Bladder Cancer Cells
    G C A T T A C G G C A T genes Article Downregulation of Cell Cycle and Checkpoint Genes by Class I HDAC Inhibitors Limits Synergism with G2/M Checkpoint Inhibitor MK-1775 in Bladder Cancer Cells Michèle J. Hoffmann * , Sarah Meneceur †, Katrin Hommel †, Wolfgang A. Schulz and Günter Niegisch Department of Urology, Medical Faculty, Heinrich-Heine-University Duesseldorf, Moorenstr. 5, 40225 Duesseldorf, Germany; [email protected] (S.M.); [email protected] (K.H.); [email protected] (W.A.S.); [email protected] (G.N.) * Correspondence: [email protected]; Tel.: +49-21-1811-5847 † Contributed equally. Abstract: Since genes encoding epigenetic regulators are often mutated or deregulated in urothelial carcinoma (UC), they represent promising therapeutic targets. Specifically, inhibition of Class-I histone deacetylase (HDAC) isoenzymes induces cell death in UC cell lines (UCC) and, in contrast to other cancer types, cell cycle arrest in G2/M. Here, we investigated whether mutations in cell cycle genes contribute to G2/M rather than G1 arrest, identified the precise point of arrest and clarified the function of individual HDAC Class-I isoenzymes. Database analyses of UC tissues and cell lines revealed mutations in G1/S, but not G2/M checkpoint regulators. Using class I-specific HDAC inhibitors (HDACi) with different isoenzyme specificity (Romidepsin, Entinostat, RGFP966), cell cycle arrest was shown to occur at the G2/M transition and to depend on inhibition of HDAC1/2 Citation: Hoffmann, M.J.; rather than HDAC3. Since HDAC1/2 inhibition caused cell-type-specific downregulation of genes Meneceur, S.; Hommel, K.; Schulz, encoding G2/M regulators, the WEE1 inhibitor MK-1775 could not overcome G2/M checkpoint W.A.; Niegisch, G.
    [Show full text]
  • Absence of Wee1 Ensures the Meiotic Cell Cycle in Xenopus Oocytes
    Downloaded from genesdev.cshlp.org on September 29, 2021 - Published by Cold Spring Harbor Laboratory Press Absence of Wee1 ensures the meiotic cell cycle in Xenopus oocytes Nobushige Nakajo,1 Satoshi Yoshitome,1 Jun Iwashita,1,2 Maki Iida, Katsuhiro Uto, Shuichi Ueno, Kengo Okamoto, and Noriyuki Sagata3 Department of Biology, Graduate School of Science, Kyushu University, Fukuoka 812-8581, Japan Meiotic cells undergo two successive divisions without an intervening S phase. However, the mechanism of S-phase omission between the two meiotic divisions is largely unknown. Here we show that Wee1, a universal mitotic inhibitor, is absent in immature (but not mature) Xenopus oocytes, being down-regulated specifically during oogenesis; this down-regulation is most likely due to a translational repression. Even the modest ectopic expression of Wee1 in immature (meiosis I) oocytes can induce interphase nucleus reformation and DNA replication just after meiosis I. Thus, the presence of Wee1 during meiosis I converts the meiotic cell cycle into a mitotic-like cell cycle having S phase. In contrast, Myt1, a Wee1-related kinase, is present and directly involved in G2 arrest of immature oocytes, but its ectopic expression has little effect on the meiotic cell cycle. These results strongly indicate that the absence of Wee1 in meiosis I ensures the meiotic cell cycle in Xenopus oocytes. Based on these results and the data published previously in other organisms, we suggest that absence of Wee1 may be a well-conserved mechanism for omitting interphase or S phase between the two meiotic divisions. [Key Words: Cell cycle; meiosis; Mos; S phase; Wee1; Xenopus oocyte] Received November 9, 1999; revised version accepted December 14, 1999.
    [Show full text]
  • Phosphatases Reverse P53-Mediated Cell Cycle Checkpoints
    COMMENTARY Phosphatases reverse p53-mediated cell cycle checkpoints Lawrence A. Donehower1 for the damage or dysfunction to be repaired Departments of Molecular Virology and Microbiology, Molecular, and Cellular Biology, Pediatrics without being transmitted to progeny cells. and the Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030 Thus, p53 has been called the “guardian of the genome” (3).Giventheimportanceof p53 as a cellular failsafe mechanism, it is The Cancer Genome Atlas and other large- In the normal cell, the p53 protein func- not surprising that its inactivation is a highly scale cancer genome sequencing projects tions as a stress integrator that becomes selected event in cancer progression. have identified an impressive number of activated in response to myriad dysfunctional Activated p53 can halt cell division in both states (e.g., damaged DNA, aberrant onco- significantly mutated genes that are likely the G1 and G2 phases of the cell division genic signaling, and hypoxia). Once activated, drivers of cancer progression (1). These stud- cycle. G1 is the preparation phase of the cell p53 can initiate stress response programs to ies have definitively confirmed that the gene before replication of its DNA and G2 pre- eliminate the dysfunctional state, such as encoding the p53 tumor suppressor is the pares the cell for mitosis. Arrest and repair of repair of DNA damage. If the stressed cell most frequently mutated gene in human can- cells before DNA replication or mitosis are is dividing, p53 can enact any one of several cers. A major component of the p53 antican- likely to prevent damage-induced mutational antiproliferative programs.
    [Show full text]
  • A Haploid Genetic Screen Identifies the G1/S Regulatory Machinery As a Determinant of Wee1 Inhibitor Sensitivity
    A haploid genetic screen identifies the G1/S regulatory machinery as a determinant of Wee1 inhibitor sensitivity Anne Margriet Heijinka, Vincent A. Blomenb, Xavier Bisteauc, Fabian Degenera, Felipe Yu Matsushitaa, Philipp Kaldisc,d, Floris Foijere, and Marcel A. T. M. van Vugta,1 aDepartment of Medical Oncology, University Medical Center Groningen, University of Groningen, 9723 GZ Groningen, The Netherlands; bDivision of Biochemistry, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands; cInstitute of Molecular and Cell Biology, Agency for Science, Technology and Research, Proteos#3-09, Singapore 138673, Republic of Singapore; dDepartment of Biochemistry, National University of Singapore, Singapore 117597, Republic of Singapore; and eEuropean Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, 9713 AV Groningen, The Netherlands Edited by Stephen J. Elledge, Harvard Medical School, Boston, MA, and approved October 21, 2015 (received for review March 17, 2015) The Wee1 cell cycle checkpoint kinase prevents premature mitotic Wee1 kinase at tyrosine (Tyr)-15 to prevent unscheduled Cdk1 entry by inhibiting cyclin-dependent kinases. Chemical inhibitors activity (5, 6). Conversely, timely activation of Cdk1 depends on of Wee1 are currently being tested clinically as targeted anticancer Tyr-15 dephosphorylation by one of the Cdc25 phosphatases drugs. Wee1 inhibition is thought to be preferentially cytotoxic in (7–10). When DNA is damaged, the downstream DNA damage p53-defective cancer cells. However, TP53 mutant cancers do not response (DDR) kinases Chk1 and Chk2 inhibit Cdc25 phos- respond consistently to Wee1 inhibitor treatment, indicating the phatases through direct phosphorylation, which blocks Cdk1 existence of genetic determinants of Wee1 inhibitor sensitivity other activation (11–13).
    [Show full text]