title: Stxbp4 regulates DeltaNp63 stability by suppression of RACK1-dependent degradation.
abstract: p63, a member of the p53 tumor suppressor family, is essential for the development of epidermis as well as other stratified epithelia. Collective evidence indicates that DeltaNp63 proteins, the N-terminally deleted versions of p63, are essential for the proliferation and survival of stratified epithelial cells and squamous cell carcinoma cells. But in response to DNA damage, DeltaNp63 proteins are quickly downregulated in part through protein degradation. To elucidate the mechanisms by which DeltaNp63 proteins are maintained at relatively high levels in proliferating cells but destabilized in response to stress, we sought to identify p63 interactive proteins that regulate p63 stability. We found that Stxbp4 and RACK1, two scaffold proteins, play central roles in balancing DeltaNp63 protein levels. While Stxbp4 functions to stabilize DeltaNp63 proteins, RACK1 targets DeltaNp63 for degradation. Under normal growth conditions, Stxbp4 is indispensable for maintaining high basal levels of DeltaNp63 and preventing RACK1-mediated p63 degradation. Upon genotoxic stress, however, Stxbp4 itself is downregulated, correlating with DeltaNp63 destabilization mediated in part by RACK1. Taken together, we have delineated key mechanisms that regulate DeltaNp63 protein stability in vivo.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Li
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Peart
authors.forename: Carol
authors.initials: C
authors.lastname: Prives
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D049109:Cell Proliferation; D016922:Cellular Senescence; D004249:DNA Damage; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D009363:Neoplasm Proteins; D020033:Protein Isoforms; C419368:RACK1 protein, human; D034741:RNA, Small Interfering; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; C498469:STXBP4 protein, human; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D033921:Vesicular Transport Proteins; C432966:ITCH protein, human; D044767:Ubiquitin-Protein Ligases; D019204:GTP-Binding Proteins