title: 5-Aza-2'-deoxycytidine reactivates gene expression via degradation of pRb pocket proteins.
abstract: Not only does 5-aza-2'-deoxycytidine (5-aza-CdR) induce the reexpression of silenced genes through the demethylation of CpG islands, but it increases the expression of unmethylated genes. However, the mechanism by which 5-aza-CdR activates the expression of genes is not completely understood. Here, we report that the pRb pocket proteins pRb, p107, and p130 were degraded in various cancer cell lines in response to 5-aza-CdR treatment, and this effect was dependent on the proteasome pathway. Mouse double minute 2 (MDM2) played a critical role in this 5-aza-CdR-induced degradation of pRb. Furthermore, PP2A phosphatase-induced MDM2 dephosphorylation at S260 was found to be essential for MDM2 binding to pRb in the presence of 5-aza-CdR. pRb degradation resulted in the significant reexpression of several genes, including methylated CDKN2A, RASFF1A, and unmethylated CDKN2D. Finally, knockdown of pRb pocket proteins by either RNAi or 5-aza-CdR treatment induced a significant decrease in the recruitment of SUV39H1 and an increase in the enrichment of KDM3B and KDM4A to histones around the promoter of RASFF1A and thus reduced H3K9 di- and trimethylation, by which RASFF1A expression is activated. Our data reveal a novel mechanism by which 5-aza-CdR induces the expression of both methylated and unmethylated genes by degrading pRb pocket proteins.
authors: Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing, China.
authors: Zhixing
authors: Z
authors: Zheng
authors: Lian
authors: L
authors: Li
authors: Xiangyu
authors: X
authors: Liu
authors: Donglai
authors: D
authors: Wang
authors: Bo
authors: B
authors: Tu
authors: Lina
authors: L
authors: Wang
authors: Haiying
authors: H
authors: Wang
authors: Wei-Guo
authors: WG
authors: Zhu
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D020868:Gene Silencing / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms; D012516:Osteosarcoma; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107 / Q000235:genetics / Q000378:metabolism*; D050717:Retinoblastoma-Like Protein p130 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000964:Antimetabolites, Antineoplastic; D006657:Histones; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D000077209:Decitabine; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D054648:Protein Phosphatase 2; D001374:Azacitidine