E2F4-RB and E2F4-p107 complexes suppress gene expression by transforming growth factor beta through E2F binding sites
E2F4-RB and E2F4-p107 complexes suppress gene expression by transforming growth factor beta through E2F binding sites
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DOI：
10.1073/pnas.94.10.4948
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发表时间：
1997-05-13
影响因子：
11.1
通讯作者：
Wang, XF
中科院分区：
文献类型：
--
作者：
Li, JM;Hu, PPC;Wang, XF
转化生长因子β在大多数细胞类型中，TGF-β导致生长停滞，TGF-β诱导视网膜母细胞瘤易感基因1产物（RE）的低磷酸化，其螯合细胞周期进入S期所需的E2 F因子，从而导致细胞周期停滞在G（1），然而，TGF-β诱导的E2 F-RB复合物可结合E2 F位点并抑制其启动子含有E2 F结合位点的特定基因的表达，我们在此表明，HaCaT细胞的TGF-β处理诱导了E2 F4-RB和E2 F4-p107复合物的形成，这些复合物能够与E2 F位点结合，在E2 F位点的突变破坏它们与DNA的结合并没有改变在循环HaCaT细胞中E2 F1，B-myb或HsORC 1基因启动子的表达。然而，在用TGF-β处理的细胞中，相同的突变刺激所有三种启动子的5至6倍的高表达。这些结果表明，E2 F结合位点在TGF-β处理下这些基因的转录抑制中起重要作用，与它们对TGF-β诱导的基因表达的抑制一致，将E2 F位点引入细胞周期蛋白依赖性激酶抑制剂p15（INK 4 B）基因的启动子有效地抑制了TGF-β对其的诱导，利用Gal 4-RB和Gal 4-p107嵌合构建体的实验表明，RE或p107在通过Gal 4 DNA结合位点连接到p15（INK 4 B）启动子时可以直接抑制TGF-β对p15（INK 4 B）基因的诱导。因此，E2 F的功能是将RE和p107带到E2 F位点，并通过TGF-β抑制基因表达。这些结果定义了E2 F4-RB和E2 F4-p107复合物在TGF-β处理下的基因抑制中的特定功能，这可能构成TGF-β诱导的生长停滞程序的组成部分。
Transforming growth factor beta (TGF-beta) causes growth arrest in most cell types, TGF-beta induces hypophosphorylation of retinoblastoma susceptibility gene 1 product (RE), which sequesters E2F factors needed for progression into S phase of the cell cycle, thereby leading to cell cycle arrest at G(1), It is possible, however, that the E2F-RB complex induced by TGF-beta may bind to E2F sites and suppress expression of specific genes whose promoters contain E2F binding sites, We show here that TGF-beta treatment of HaCaT cells induced the formation of E2F4-RB and E2F4-p107 complexes, which are capable of binding to E2F sites, Disruption of their binding to DNA with mutation in the E2F sites did not change the expression from promoters of E2F1, B-myb, or HsORC1 genes in cycling HaCaT cells. However, the same mutation stimulated 5- to 6-fold higher expression from all three promoters in cells treated with TGF-beta, These results suggest that E2F binding sites play an essential role in the transcription repression of these genes under TGF-beta treatment, Consistent with their repression of TGF-beta-induced gene expression, introduction of E2F sites into the promoter of cyclin-dependent kinase inhibitor p15(INK4B) gene effectively inhibited its induction by TGF-beta, Experiments utilizing Gal4-RB and Gal4-p107 chimeric constructs demonstrated that either RE or p107 could directly repress TGF-beta induction of p15(INK4B) gene when tethered to p15(INK4B) promoter through Gal4 DNA binding sites. Therefore, E2F functions to bring RE and p107 to E2F sites and represses gene expression by TGF-beta, These results define a specific function for E2F4-RB and E2F4-p107 complexes in gene repression under TGF-beta treatment, which may constitute an integral part of the TGF-beta-induced growth arrest program.