The hormone-bound vitamin D receptor regulates turnover of target proteins of the SCFFBW7 E3 ligase By Reyhaneh Salehi Tabar Department of Experimental Medicine McGill University Montreal, QC, Canada April 2016 A thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Doctor of Philosophy © Reyhaneh Salehi Tabar 1 Table of Contents Abbreviations ................................................................................................................................................ 7 Abstract ....................................................................................................................................................... 10 Rèsumè ....................................................................................................................................................... 13 Acknowledgements ..................................................................................................................................... 16 Preface ........................................................................................................................................................ 17 Contribution of authors .............................................................................................................................. 18 Chapter 1-Literature review........................................................................................................................ 20 1.1. General introduction and overview of thesis ............................................................................. 20 1.2. 1,25D signaling ................................................................................................................................. 21 1.2.1 The vitamin D receptor .................................................................................................................. 23 1.2.2. Non-genomic actions of 1,25D...................................................................................................... 24 1.2.3. Genomic action of 1,25D .............................................................................................................. 24 1.2.4. 1,25D-mediated Transcriptional activation .................................................................................. 25 1.2.5. 1,25D-mediated Transcriptional repression ................................................................................. 25 1.2.6. 1,25D signaling in cancer .............................................................................................................. 26 1.2.7. Anti-proliferative effects of 1,25D ................................................................................................ 26 1.2.8. Induction of apoptosis by 1,25D ................................................................................................... 27 1.2.9. 1,25D pro-differentiating effects .................................................................................................. 27 1.2.10. 1,25D anti-Inflammatory effects ................................................................................................. 27 1.2.11. Inhibition of invasion and metastasis by 1,25D .......................................................................... 28 1.3. c-Myc Transcription Factor .............................................................................................................. 28 1.3.1. MYC gene ...................................................................................................................................... 29 1.3.2. c-Myc protein ................................................................................................................................ 31 1.3.3. c-Myc regulation ........................................................................................................................... 32 1.3.3.1. Regulation of MYC transcription ................................................................................................ 33 1.3.3.2. MYC mRNA stability regulation .................................................................................................. 34 1.3.3.3. c-Myc Protein stability regulation .............................................................................................. 36 1.3.3.3.1. c-Myc Modifications ............................................................................................................... 36 1.3.3.3.1.1. Ubiquitination of c-Myc ....................................................................................................... 38 1.3.3.3.1.1.1. Ubiquitination and c-Myc degradation ............................................................................. 38 1.3.3.3.1.1.1.1. Ubiquitination by FBW7 ................................................................................................. 38 1.3.3.3.1.1.2. Ubiquitination for stabilization or activation .................................................................... 40 2 1.3.4. Transcriptional activation by c-Myc .............................................................................................. 40 1.3.5. Transcriptional repression by c-Myc ............................................................................................. 41 1.3.6. DNA binding of c-Myc ................................................................................................................... 41 1.3.7. Functions of c-Myc ........................................................................................................................ 42 1.3.7.1. Cell cycle regulation by c-Myc ................................................................................................... 43 1.3.7.2. Apoptosis induction by c-Myc .................................................................................................... 45 1.3.8. c-Myc Deregulation in Cancer ....................................................................................................... 45 1.3.8.1. MYC Mutations in Cancer .......................................................................................................... 48 1.3.8.2. c-Myc Signaling in Cancer .......................................................................................................... 49 1.4. MAX protein ..................................................................................................................................... 49 1.4.1. c-Myc/MAX/MXD1 network ......................................................................................................... 50 1.5. MXD1 Transcription Factor .............................................................................................................. 50 1.5.1. MXD1 cofactors antagonize c-Myc cofactors ............................................................................... 51 1.5.2. Regulation of proliferation and apoptosis by MXD1 .................................................................... 51 1.5.3. Regulation of MXD1 transcription ................................................................................................ 52 1.5.4. Regulation of MXD1 protein ......................................................................................................... 53 1.6. Protein ubiquitination ...................................................................................................................... 53 1.6.1. Ubiquitin Proteasome System (UPS) ............................................................................................. 54 1.6.1.1. Proteasome complex ................................................................................................................. 54 1.6.1.2. Ubiquitin .................................................................................................................................... 55 1.6.2. E3 ligases ....................................................................................................................................... 56 1.6.2.1. HECT domain E3s ....................................................................................................................... 57 1.6.2.2. RING finger E3s .......................................................................................................................... 57 1.6.2.2.1. Multi-subunit RING finger E3s ................................................................................................ 58 1.6.2.2.1.1. Cullin Ring Ligases (CRLs) ..................................................................................................... 58 1.6.2.2.2. RING-IBR-RING E3s .................................................................................................................. 59 1.6.2.3. U-Box proteins ........................................................................................................................... 60 1.6.3. Substrate recognition mediator in SCF E3 ligase complex ............................................................ 60 1.6.3.1. F-Box proteins ............................................................................................................................ 60 1.6.3.1.1. FBW7 ....................................................................................................................................... 61 1.6.3.1.1.1. FBW7 gene and isoforms ..................................................................................................... 61 1.6.3.1.1.2. FBW7 and GSK3s .................................................................................................................