title: Negative regulation of the deacetylase SIRT1 by DBC1.
abstract: SIRT1 is an NAD-dependent deacetylase critically involved in stress responses, cellular metabolism and, possibly, ageing. The tumour suppressor p53 represents the first non-histone substrate functionally regulated by acetylation and deacetylation; we and others previously found that SIRT1 promotes cell survival by deacetylating p53 (refs 4-6). These results were further supported by the fact that p53 hyperacetylation and increased radiation-induced apoptosis were observed in Sirt1-deficient mice. Nevertheless, SIRT1-mediated deacetylase function is also implicated in p53-independent pathways under different cellular contexts, and its effects on transcriptional factors such as members of the FOXO family and PGC-1alpha directly modulate metabolic responses. These studies validate the importance of the deacetylase activity of SIRT1, but how SIRT1 activity is regulated in vivo is not well understood. Here we show that DBC1 (deleted in breast cancer 1) acts as a native inhibitor of SIRT1 in human cells. DBC1-mediated repression of SIRT1 leads to increasing levels of p53 acetylation and upregulation of p53-mediated function. In contrast, depletion of endogenous DBC1 by RNA interference (RNAi) stimulates SIRT1-mediated deacetylation of p53 and inhibits p53-dependent apoptosis. Notably, these effects can be reversed in cells by concomitant knockdown of endogenous SIRT1. Our study demonstrates that DBC1 promotes p53-mediated apoptosis through specific inhibition of SIRT1.
authors.affiliation: Institute for Cancer Genetics, and Department of Pathology College of Physicians and Surgeons, Columbia University, 1130 St Nicholas Avenue, New York, New York 10032, USA.
authors.forename: Wenhui
authors.initials: W
authors.lastname: Zhao
authors.forename: Jan-Philipp
authors.initials: JP
authors.lastname: Kruse
authors.forename: Yi
authors.initials: Y
authors.lastname: Tang
authors.forename: Sung Yun
authors.initials: SY
authors.lastname: Jung
authors.forename: Jun
authors.initials: J
authors.lastname: Qin
authors.forename: Wei
authors.initials: W
authors.lastname: Gu
mesh_terms: D000107:Acetylation; D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D045744:Cell Line, Tumor; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D056564:Sirtuin 1; D037761:Sirtuins / Q000037:antagonists & inhibitors* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C527450:CCAR2 protein, human; D034741:RNA, Small Interfering; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D037761:Sirtuins