Yang Weiwen, Wetterskog Daniel, Matsumoto Yoshiki, Funa Keiko
Department of Medical Chemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden.
Int J Cancer. 2008 Nov 1;123(9):2020-30. doi: 10.1002/ijc.23735.
Herein, we show that both exogenously transfected and endogenously activated p53 repress promoter activity and expression of PDGFRB. p53 binds the proximal promoter containing the CCAAT motif as examined by EMSA and chromatin immunoprecipitation. However, gradual induction of p53 in tet-onSAOS2 cells resulted in a transient increase of the PDGFRB-promoter activity and its expression. As binding of p53 to the promoter increased, previously bound p73, DeltaNp73, c-Myc, HDAC1 and HDAC4 were dismissed from the repressed promoter, and p300 was recruited. The transient increase of the promoter activity was therefore induced by the release of the p73, Myc and HDACs, previously shown to act as repressors to this promoter. Along with further increase of p53, p300 was replaced by HDAC1 and HDAC4, resulting in decreased PDGFRB expression. For the repression, acetylation of the C-terminal lysines of p53 is important, and both acetyl-K373p53 and methyl-K370p53 became bound to the promoter. The acetyl-K373p53 was accumulated in the nucleus and colocalized with promyelocytic leukemia protein. Mitomycin treatment of MEF induced similar epigenetic modification of p53 and its binding to the promoter chromatin. Addition of a PDGFR tyrosine-kinase inhibitor to p53-inducing tet-onSAOS2 increased the number of apoptotic cells. These results suggest that p53 represses the PDGFRB promoter, facilitating the p53-induced apoptosis, whereas tumor cells with p53 mutation or a high level of DeltaNp73 or Myc could become refractory to the regulation.
在此，我们表明外源性转染和内源性激活的p53均能抑制血小板衍生生长因子受体β（PDGFRB）的启动子活性和表达。通过电泳迁移率变动分析（EMSA）和染色质免疫沉淀检测发现，p53与含有CCAAT基序的近端启动子结合。然而，在四环素调控的SAOS2细胞中逐渐诱导p53会导致PDGFRB启动子活性及其表达的短暂增加。随着p53与启动子的结合增加，先前结合的p73、ΔNp73、c-Myc、组蛋白去乙酰化酶1（HDAC1）和组蛋白去乙酰化酶4（HDAC4）从受抑制的启动子上解离，并且募集了p300。因此，启动子活性的短暂增加是由先前显示对该启动子起抑制作用的p73、Myc和HDACs的释放所诱导的。随着p53的进一步增加，p300被HDAC1和HDAC4取代，导致PDGFRB表达降低。对于这种抑制作用，p53 C末端赖氨酸的乙酰化很重要，并且乙酰化的K373p53和甲基化的K370p53均与启动子结合。乙酰化的K373p53在细胞核中积累并与早幼粒细胞白血病蛋白共定位。丝裂霉素处理小鼠胚胎成纤维细胞（MEF）诱导了p53类似的表观遗传修饰及其与启动子染色质的结合。向诱导p53的四环素调控SAOS2细胞中添加PDGFR酪氨酸激酶抑制剂会增加凋亡细胞的数量。这些结果表明，p53抑制PDGFRB启动子，促进p53诱导的细胞凋亡，而具有p53突变或高水平的ΔNp73或Myc的肿瘤细胞可能对这种调控产生抗性。
