Interchangeable Roles for E2F Transcriptional Repression by the Retinoblastoma Protein and p27KIP1-Cyclin-Dependent Kinase Regulation in Cell Cycle Control and Tumor Suppression.
The mammalian G1-S phase transition is controlled by the opposing forces of cyclin-dependent kinases (CDK) and the retinoblastoma protein (pRB). Here, we present evidence for systems-level control of cell cycle arrest by pRB-E2F and p27-CDK regulation. By introducing a point mutant allele of pRB that is defective for E2F repression (Rb1G) into a p27KIP1null background (Cdkn1b-/-), both E2F transcriptional repression and CDK regulation are compromised. These double-mutant Rb1G/G; Cdkn1b-/-mice are viable and phenocopy Rb1+/-mice in developing pituitary adenocarcinomas, even though neither single mutant strain is cancer prone. Combined loss of pRB-E2F transcriptional regulation and p27KIP1leads to defective proliferative control in response to various types of DNA damage. In addition, Rb1G/G; Cdkn1b-/-fibroblasts immortalize faster in culture and more frequently than either single mutant genotype. Importantly, the synthetic DNA damage arrest defect caused by Rb1G/G; Cdkn1b-/-mutations is evident in the developing intermediate pituitary lobe where tumors ultimately arise. Our work identifies a unique relationship between pRB-E2F and p27-CDK control and offers in vivo evidence that pRB is capable of cell cycle control through E2F-independent effects.
London Regional Cancer Program, Western University, London, Ontario, Canada.|Department of Biochemistry, Western University, London, Ontario, Canada.
Michael J
MJ
Thwaites
London Regional Cancer Program, Western University, London, Ontario, Canada.|Department of Biochemistry, Western University, London, Ontario, Canada.
Matthew J
MJ
Cecchini
London Regional Cancer Program, Western University, London, Ontario, Canada.|Department of Biochemistry, Western University, London, Ontario, Canada.
Daniel T
http://orcid.org/0000-0002-3530-2821
DT
Passos
Veterinary Services, Western University, London, Ontario, Canada.
Ian
I
Welch
London Regional Cancer Program, Western University, London, Ontario, Canada fdick@uwo.ca.|Children's Health Research Institute, Western University, London, Ontario, Canada.|Department of Biochemistry, Western University, London, Ontario, Canada.
Frederick A
FA
Dick
D000818:Animals; D059447:Cell Cycle Checkpoints; D002461:Cell Line, Transformed; D016895:Culture Media, Serum-Free; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis; D004249:DNA Damage; D050684:E2F Transcription Factors / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism; D051379:Mice; D009154:Mutation / Q000235:genetics; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology*; D018384:Oxidative Stress; D010902:Pituitary Gland / Q000196:embryology / Q000378:metabolism; D014176:Protein Biosynthesis / Q000235:genetics; D055550:Protein Stability; D011836:Radiation Tolerance; D016160:Retinoblastoma Protein / Q000378:metabolism*; D014158:Transcription, Genetic
D016895:Culture Media, Serum-Free; D050684:E2F Transcription Factors; D016160:Retinoblastoma Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA
CDK; DNA damage; DNA damage checkpoints; E2F; cell cycle; cyclin-dependent kinases; tumor suppressor; tumor suppressor genes