Nijmegen Breakage Syndrome Disease Protein and MRE11 at PML Nuclear Bodies and Meiotic Telomeres1

[CANCER RESEARCH 60, 2331–2334, May 1, 2000] Advances in Brief

David B. Lombard and Leonard Guarente2 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

Abstract prostate cancer or chronic testicular pain, or from 129/BALB mice; indirect immunofluorescence was performed as for fibroblasts. Nijmegen breakage syndrome is a disease characterized by immuno- Immunofluorescence. Two days prior to fixation, cells were split at vary- deficiency, genomic instability, and cancer susceptibility. The gene prod- ing dilutions onto multiwell slides (Cellpoint). Eight h prior to fixation, some uct defective in Nijmegen breakage syndrome, p95, associates with two slides were exposed to 10 Gy of IR and then returned to the incubator. WI38 other proteins, MRE11 and RAD50. Here we demonstrate that in the and NBS fibroblasts were grown on the same slide to ensure uniformity of the absence of DNA damage, a portion of p95 and MRE11 is concentrated in culture conditions. Slides were prepared using the CSK and PFA fixation PML nuclear bodies (NBs); MRE11 localization to the NBs is p95-depend- method as described previously (14, 15). Briefly, slides were washed once in ent. In mammalian meiocytes, these proteins are specifically found at the PBS, washed for 30 s in CSK [100 mM NaCl, 300 mM sucrose, 3 mM MgCl2, telomeres. These results implicate the NBs in the maintenance of genomic 10 mM PIPES (pH 6.8)], incubated for 2 min in CSK containing 0.5% Triton stability and suggest that p95 and MRE11 may have roles in telomere X-100, washed briefly in CSK, and then fixed in PBS containing 4% PFA maintenance in mammals, analogous to the role their homologues play in (Electron Microscopy Sciences) for 10 min. yeast. Primary antibodies and their dilutions were as follows: rabbit anti-p95 and Introduction rabbit anti-MRE11 (gifts of J. Petrini, University of Wisconsin; a subsequent aliquot was the gift of D. Hill, Oncogene Research, Boston, MA), both 1:200 NBS3 is a rare autosomal recessive disease. Affected individuals dilutions; mouse monoclonal anti-PML (Santa Cruz), 1:100 dilution; rabbit demonstrate delayed growth, microcephaly and mental retardation, anti-SCP3 (gift of Christa Heyting), 1:200 dilution; 3H3 mouse anti-SCP3 (gift variable immunodeficiency, gonadal dysfunction, and heightened sus- of Christa Heyting), 1:2 dilution; PX1 mouse anti-MRE11 (GeneTex), 1:50 dilution; mouse anti-TRF1 (gift of Titia deLange, Rockefeller University, NY), ceptibility to cancer (1). Cells explanted from individuals with this 1:5000 dilution. Slides were preincubated in blocking buffer [PBS containing disease show genomic instability and sensitivity to IR, and lack an 0.2% cold water fish skin gelatin (Sigma), 5% goat serum, and 0.2% Tween appropriate G1-S checkpoint in response to DNA damage (2–6). The 20] for 30 min and then incubated for1hinblocking buffer containing the gene product defective in NBS is p95/Nibrin (hereinafter referred to indicated concentration of primary antibody (or antibodies) at 37°C in a as p95; Refs. 7–9). p95 is present in a complex with at least two other humidity chamber. Slides were then washed three times for 5 min each in PBS proteins, MRE11 and RAD50 (7). Immunofluorescent localization of containing 0.2% Tween 20 and then incubated in blocking buffer plus sec- MRE11, RAD50, and p95 in mammalian cells provides additional ondary antibody. All secondary antibodies were purchased from Vector and evidence that these proteins respond to DNA damage (7, 10). In the were used at 1:100 dilution with the exception of Cy3 antirabbit and Cy3 absence of damage, these proteins have been reported to be diffusely antimouse, which were purchased from Amersham-Pharmacia and used at spread throughout the nucleoplasm. After treatment of cells with IR, 1:200 dilution. Typical results are shown. In all cases, control experiments were performed using each primary alone and both secondaries to verify the all three proteins colocalize in numerous nuclear dots, termed IR- results obtained in the double-labeling experiments. induced foci. This response is absent in cells derived from NBS patients (7). Experiments in yeast have implicated MRE11p and Results RAD50p in telomere maintenance (11, 12), although no telomeric role for these proteins has yet been demonstrated in mammals. Here we p95 and MRE11 at PML NBs in Somatic Fibroblasts. The p95 demonstrate that in the absence of irradiation, a fraction of p95 and protein previously has been shown to be present throughout the MRE11 proteins is present at PML NBs in human mitotic cells. In nucleus of nonirradiated cells. However, if cells are initially subject to addition, in mammalian meiocytes, these proteins are associated with a hypotonic preextraction prior to fixation, which removes some of the telomeres. diffuse nucleoplasmic p95, a fraction of p95 is concentrated in dis- crete nuclear structures in nonirradiated WI38 primary human fibro- Materials and Methods blasts (Fig. 1A). Using different preextraction protocols, others have Cells. The wild-type human fibroblast WI38 and the NBS mutant cell line also observed concentration of p95 in nuclear foci in nonirradiated GM07166 were obtained from the Coriell Institute for Medical Research. Cells cells.4 The appearance of these p95 foci is similar to PML NBs. were grown in DMEM/15% heat-inactivated fetal bovine serum. Costaining of WI38 fibroblasts with rabbit anti-p95 and mouse anti- Meiotic Preparations. Meiotic spreads were prepared by standard tech- PML demonstrated that these p95 foci are NBs and that the p95 and niques (13) from testes removed from patients suffering from metastatic PML staining patterns are virtually coincident in nonirradiated cells. Identical results were obtained using a human antiserum derived from Received 1/20/00; accepted 3/20/00. a patient with primary biliary cirrhosis containing a high titer of The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with antibodies directed against NBs (data not shown). Under these con- 18 U.S.C. Section 1734 solely to indicate this fact. ditions, numerous other antigens, including Rad51, do not localize to 1 D. B. L was supported by an MSTP grant to Harvard Medical School. The Guarente NBs. With previously published immunofluorescence methods (7, laboratory is supported by grants from the NIH, The Ellison Medical Foundation, The Seaver Institute, and The Howard and Linda Stern Foundation. 10), these p95 foci are nearly totally obscured by diffuse nuclear p95 2 To whom requests for reprints should be addressed, at Department of Biology, staining (data not shown). Massachusetts Institute of Technology, Cambridge, MA 02139. E-mail: [email protected]. 3 The abbreviations used are: NBS, Nijmegen breakage syndrome; IR, ionizing radiation; NB, nuclear body. 4 R. S. Maser and J. H. Petrini, personal communication. 2331

Fig. 1. Fractions of p95 and MRE11 localize to NBs. Shown are immunofluorescence images of wild-type primary human fibroblasts (WI38; A–C) or primary fibroblasts derived from an individual with NBS (GM07166; D) stained with anti-95 and anti-PML (A and B) or anti-MRE11 and anti-PML (C and D). In B, cells were irradiated with 10 Gy of IR from a 137Cs ␥-source and then allowed to recover for 8 h prior to fixation and staining. Extensive colocalization of focal p95 and NB staining are observed in WI38 cells (A). After ␥-irradiation, p95 appears in foci adjacent to some NBs (B, closed arrow) and also appears at additional foci not associated with NBs (B, open arrow). MRE11 is also present at NBS (C) in a p95-dependent manner (D).

DNA damage previously had been demonstrated to cause relocal- NBs (Fig. 1B, closed arrow) or not associated with any apparent NBs ization of RAD50, MRE11, and p95 to IR-induced foci (7, 10). WI38 (Fig. 1B, open arrow). Overall, the p95 and PML patterns overlapped fibroblasts were subjected to 10 Gy of ␥-irradiation and then fixed and much less well in irradiated than in nonirradiated cells. Thus ␥-irra- stained 8 h later for the presence of p95 and PML (Fig. 1B). Some diation apparently causes redistribution of NB-associated p95 from overlap was observed between p95 and PML in irradiated cells; NBs to larger domains in the nucleus, some of which abut NBs and however, a substantial amount of p95 was now observed adjacent to some of which do not. Costaining with DAPI does not reveal any 2332

Fig. 2. p95 and MRE11 localize to telomeres during murine and human meiosis. Murine meiotic spread was stained with rabbit anti-p95 and mouse anti-SCP3(A) or mouse anti-MRE11 and rabbit anti-SCP3 (B). p95 and MRE11 are associated with the distal ends of the chromosomes; MRE11 also appears to coat some chromosomes. C, staining of human meiotic spread stained with rabbit anti-p95 and mouse anti-TRF1 confirms that these p95 foci represent telomeres. obvious relationship between these larger p95-containing domains early pachynema (data not shown). To confirm these results, MRE11 and heterochromatic regions (Fig. 1B). localization was also determined in these preparations using a com- The localization of MRE11 was also assessed. A fraction of mercially available monoclonal antibody against MRE11 (PX1; Gene- MRE11 also concentrated in NBs (Fig. 1C). In NBS cells, this Tex) and a polyclonal antisera directed against SCP3 (Fig. 2B). focal MRE11 staining was absent, indicating that p95 is necessary for MRE11 is seen to be concentrated at the ends of chromosomes, MRE11 localization to NBs in the absence of DNA damage (Fig. 1D). although some chromosomes are also coated by MRE11 protein. We p95 and MRE11 Proteins at Meiotic Telomeres. Localization of have observed MRE11 present on the synaptonemal complex of zero p95 and MRE11 was assayed in both mouse and human meiotic to four chromosomes per meiotic spread (Fig. 2B). We typically spreads. Immunofluorescence was performed on mouse meiotic observe this MRE11 staining in late leptonema, but we do not know spreads using anti-p95 and a monoclonal antibody (3H3) directed whether it correlates with the precise stage of the spread within against SCP3, a proteinaceous component of the presynaptic axial meiosis. elements that remains associated with the synaptonemal complex The localization of p95 and MRE11 to the ends of chromosomes following synapsis (16). p95 labeling was predominantly seen asso- during meiosis suggests that these proteins may be preferentially ciated with the very distal ends of the chromosomes (Fig. 2A). This associated with telomeres during this process. To confirm this hy- labeling was seen in meiotic spreads in late leptonema, zygonema, and pothesis, p95 and the telomere binding protein TRF1 were colocalized 2333

Downloaded from cancerres.aacrjournals.org on October 2, 2021. © 2000 American Association for Cancer Research. p95 AT MEIOTIC TELOMERES in human meiotic spreads using rabbit anti-p95 and mouse anti-TRF1. Gertler for help with microscopy; J. Petrini, R. Marciniak, D. Bloch, B. The use of human meioses was necessitated by the fact that the Johnson, R. Jaenisch, and members of the Guarente and Jaenisch laboratories anti-TRF1 antibody did not react with the murine protein. We con- for helpful discussions; and B. Johnson and R. Marciniak for comments on the firmed that the p95 staining seen at the ends of chromosomes was at manuscript. the telomeres (Fig. 2C). This pattern of p95 staining was never observed in mitotic cells. Similar overlap was observed when rabbit References anti-MRE11 and anti-TRF1 were used (data not shown). 1. Shiloh, Y. Ataxia-telangiectasia and the Nijmegen breakage syndrome: related dis- orders but genes apart. Annu. Rev. Genet., 31: 635–662, 1997. Discussion 2. 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I., Bosco, G., Ross, L. O., Evans, S. K., Salinger, A. P., Moore, J. K., Haber, J. E., and Lundblad, V. Telomere maintenance is dependent on activities trated in NBs in primary cells, also support this hypothesis. Alterna- required for end repair of double-strand breaks. Curr. Biol., 8: 657–660, 1998. tively, the NBs may simply act as a reservoir for proteins that 12. Le, S., Moore, J. K., Haber, J. E., and Greider, C. W. RAD50 and RAD51 define two pathways that collaborate to maintain telomeres in the absence of telomerase. Genet- translocate and effect their functions in other locations throughout the ics, 152: 143–152, 1999. cell. The observation that p95 and MRE11 relocalize in response to 13. Peters, A. H., Plug, A. W., van Vugt, M. J., and de Boer, P. A drying-down technique DNA damage supports this notion. for the spreading of mammalian meiocytes from the male and female germline. Chromosome Res., 5: 66–68, 1997. Although MRE11 and RAD50 proteins recently have been shown to 14. Cardoso, M. C., Leonhardt, H., and Nadal-Ginard, B. Reversal of terminal differen- be expressed during meiosis (23), this is the first demonstration that p95 tiation and control of DNA replication: cyclin A and Cdk2 specifically localize at and MRE11 are specifically present on telomeres during this process; subnuclear sites of DNA replication. Cell, 74: 979–992, 1993. 15. Marciniak, R. A., Lombard, D. B., Johnson, F. B., and Guarente, L. Nucleolar moreover, it is the first demonstration of any telomere-associated proteins localization of the Werner syndrome protein in human cells. Proc. Natl. Acad. Sci. in mammalian meiosis to our knowledge. Genetic studies in yeast suggest USA, 95: 6887–6892, 1998. 16. Lammers, J. H., Offenberg, H. H., van Aalderen, M., Vink, A. C., Dietrich, A. J., and roles for MRE11p, RAD50p, and the p95 homologue Xrs2p in telomere Heyting, C. The gene encoding a major component of the lateral elements of maintenance (11, 12). 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Biochem., 63: of chromosomes in mitotic cells, rendering them suitable substrates for 280–291, 1996. 19. Ishov, A. M., and Maul, G. G. The periphery of nuclear domain 10 (ND10) as site of telomerase (11). High levels of telomerase are found in the testes of M. DNA virus deposition. J. Cell Biol., 134: 815–826, 1996. musculus (24). It is possible that the telomere-associated p95 and MRE11 20. Korioth, F., Maul, G. G., Plachter, B., Stamminger, T., and Frey, J. The nuclear we observed are responsible for processing the telomeres to a telomerase- domain 10 (ND10) is disrupted by the human cytomegalovirus gene product IE1. Exp. Cell Res., 229: 155–158, 1996. accessible form. It will be interesting to study whether these proteins are 21. Yeager, T. R., Neumann, A. A., Englezou, A., Huschtscha, L. I., Noble, J. R., and also associated with telomeres in telomerase-positive somatic stem cells. Reddel, R. R. Telomerase-negative immortalized human cells contain a novel type of promyelocytic leukemia (PML) body. Cancer Res., 59: 4175–4179, 1999. Acknowledgments 22. Johnson, F. B., Lombard, D. B., Neff, N. F., Mastrangelo, M-A., Dewolf, W., Ellis, N. A., Marciniak, R. A., Yin, Y., Jaenisch, R., and Guarente, L. Association of the Bloom Syndrome protein with topoisomerase III␣ in somatic and meiotic cells. We thank the following individuals for their generous contributions of Cancer Res., 60: 1162–1167, 2000. antibodies: J. Petrini for anti-p95 and anti-MRE11, D. Bloch for human 23. Goedecke, W., Eijpe, M., Offenberg, H. H., van Aalderen, M., and Heyting, C. anti-PML, D. Hill for an additional aliquot of anti-p95 and anti-MRE11, MRE11 and Ku70 interact in somatic cells, but are differentially expressed in early Christa Heyting for rabbit and mouse anti-SCP3, and Titia deLange for meiosis. Nat. Genet., 23: 194–198, 1999. 24. Prowse, K. R., and Greider, C. W. Developmental and tissue-specific regulation of anti-TRF1. Most of the images shown in this work were generated at the Keck mouse telomerase and telomere length. Proc. Natl. Acad. Sci. USA, 92: 4818–4822, imaging facility, Whitehead Institute, MIT. We gratefully acknowledge F. 1995.

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Downloaded from cancerres.aacrjournals.org on October 2, 2021. © 2000 American Association for Cancer Research. Nijmegen Breakage Syndrome Disease Protein and MRE11 at PML Nuclear Bodies and Meiotic Telomeres

David B. Lombard and Leonard Guarente

Cancer Res 2000;60:2331-2334.

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