title: Familial melanoma-associated mutations in p16 uncouple its tumor-suppressor functions.
abstract: Familial melanoma is associated with point mutations in the cyclin-dependent kinase (CDK) inhibitor p16(INK4A) (p16). We recently reported that p16 regulates intracellular oxidative stress in a cell cycle-independent manner. Here we constructed 12 different familial melanoma-associated point mutants spanning the p16 coding region and analyzed their capacity to regulate cell cycle phase and suppress reactive oxygen species (ROS). Compared with wild-type p16, which fully restored both functions in p16-deficient fibroblasts, various p16 mutants differed in their capacity to normalize ROS and cell cycle profiles. Although some mutations did not impair either function, others impaired both. Interestingly, several mutations impaired cell cycle (R24Q, R99P, and V126D) or oxidative functions (A36P, A57V, and P114S) selectively, indicating that these two functions of p16 can be uncoupled. Similar activities were confirmed with selected mutants in human melanoma cells. Many mutations impairing both cell cycle and oxidative functions, or only cell cycle function, localize to the third ankyrin repeat of the p16 molecule. Alternatively, most mutations impairing oxidative but not cell cycle function, or those not impairing either function, lie outside this region. These results demonstrate that particular familial melanoma-associated mutations in p16 can selectively compromise these two independent tumor-suppressor functions, which may be mediated by distinct regions of the protein.
authors.affiliation: Department of Oncological Sciences, University of Utah Health Sciences Center, Salt Lake City, UT, USA.
authors.forename: Noah C
authors.initials: NC
authors.lastname: Jenkins
authors.forename: Jae
authors.initials: J
authors.lastname: Jung
authors.forename: Tong
authors.initials: T
authors.lastname: Liu
authors.forename: Megan
authors.initials: M
authors.lastname: Wilde
authors.forename: Sheri L
authors.initials: SL
authors.lastname: Holmen
authors.forename: Douglas
authors.initials: D
authors.lastname: Grossman
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002453:Cell Cycle / Q000502:physiology; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D051379:Mice; D018384:Oxidative Stress / Q000235:genetics; D017354:Point Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology; D013329:Structure-Activity Relationship
chemical_list: C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D017382:Reactive Oxygen Species