Zhao L-J, Subramanian T, Chinnadurai G
Institute for Molecular Virology, Saint Louis University Health Sciences Center, Doisy Research Center, St Louis, MO 63104, USA.
Oncogene. 2008 Sep 4;27(39):5214-22. doi: 10.1038/onc.2008.162. Epub 2008 May 19.
The 243-residue E1A protein of adenovirus induces cellular proliferation, at least partly by regulating the transcription of cellular genes. This E1A function requires E1A N-terminal region and conserved regions 1 and 2 (CR1 and CR2), which interact with histone acetyl transferases, p400 chromatin-modifying complex and the Rb family proteins. A PLDLS motif at the E1A C-terminal (CR4) region, interacts with the C-terminal binding proteins (CtBP1 and CtBP2), and antagonizes some E1A functions. In this report, we discovered that the transcriptional activation function of E1A was specifically repressed by a short N-terminal domain unique to CtBP2. The CtBP2-mediated repression of E1A transcriptional activation activity is independent of histone deacetylases, which can be recruited by CtBP1/2 proteins to inhibit transcription. Fusion of the CtBP2 N-terminal 20 residues to the E1A C-terminal region rendered E1A to be inactive in transcriptional activation without interfering with E1A's ability to interact with major cofactors such as pRb, p400 and p300. Substitution of the N-terminal domain of CtBP1 for the CtBP2 domain in E1A-CtBP2 fusion partially restored the transactivation activity of E1A. In a cell-proliferation model utilizing primary baby rat kidney cells and retrovirally expressed E1A, the ability of E1A to induce cellular proliferation was strongly inhibited when the CtBP2 N-terminal region was fused to E1A. These results are consistent with a hypothesis that CtBP2 may inhibit E1A induced cell proliferation by antagonizing the transcriptional activation function controlled by the N-terminal region of E1A.
腺病毒的243个氨基酸残基的E1A蛋白可诱导细胞增殖，至少部分是通过调节细胞基因的转录来实现的。E1A的这种功能需要E1A的N端区域以及保守区域1和2（CR1和CR2），它们可与组蛋白乙酰转移酶、p400染色质修饰复合物和Rb家族蛋白相互作用。E1A C端（CR4）区域的一个PLDLS基序与C端结合蛋白（CtBP1和CtBP2）相互作用，并拮抗E1A的某些功能。在本报告中，我们发现E1A的转录激活功能被CtBP2特有的一个短N端结构域特异性抑制。CtBP2介导的对E1A转录激活活性的抑制独立于组蛋白去乙酰化酶，后者可被CtBP1/2蛋白招募以抑制转录。将CtBP2的N端20个残基与E1A的C端区域融合，使得E1A在转录激活中失去活性，而不影响E1A与主要辅因子如pRb、p400和p300相互作用的能力。用E1A-CtBP2融合物中CtBP1的N端结构域替换CtBP2结构域，可部分恢复E1A的反式激活活性。在利用原代新生大鼠肾细胞和逆转录病毒表达的E1A的细胞增殖模型中，当CtBP2的N端区域与E1A融合时，E1A诱导细胞增殖的能力受到强烈抑制。这些结果与一个假设一致，即CtBP2可能通过拮抗由E1A N端区域控制的转录激活功能来抑制E1A诱导的细胞增殖。
