Maldonado Edio, Cabrejos María Eugenia, Banks Lawrence, Allende Jorge E
Programa de Biologìa Celular y Molecular, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
J Cell Biochem. 2002;85(4):663-9. doi: 10.1002/jcb.10172.
Previous studies have shown that the HPV-16 E7 protein interacts with TBP. This interaction was found to take place through residues in the carboxy terminal half of E7, mutation of which resulted in weaker transforming activity. In addition, binding of E7 to TBP was found to be increased following protein kinase CK2 (casein kinase II) phosphorylation of E7, and mutation of this CK2 site also reduces E7's transforming activity. To date, however, there is no information on the effects of E7 upon TBP function. In order to address this we have performed a series of assays to investigate the effects of E7 upon the ability of human and S. pombe TBP to bind DNA. We show that HPV-16 E7 is indeed a potent inhibitor of TBP DNA binding activity. Further, this activity of E7 is increased following CK2 phosphorylation of E7, consistent with it having an increased affinity for TBP. Finally, a mutant E7 protein defective in its ability to bind TBP, has no effect upon TBP binding to DNA. These results demonstrate that one consequence of the E7-TBP interaction is abolition of TBP DNA binding activity, and may provide an explanation for the transcriptional inhibitory effects of E7.
先前的研究表明，人乳头瘤病毒16型（HPV - 16）E7蛋白与TATA盒结合蛋白（TBP）相互作用。发现这种相互作用通过E7羧基末端一半的残基发生，这些残基的突变导致转化活性减弱。此外，发现蛋白激酶CK2（酪蛋白激酶II）对E7进行磷酸化后，E7与TBP的结合增加，并且该CK2位点的突变也降低了E7的转化活性。然而，迄今为止，尚无关于E7对TBP功能影响的信息。为了解决这个问题，我们进行了一系列试验，以研究E7对人和粟酒裂殖酵母TBP结合DNA能力的影响。我们表明，HPV - 16 E7确实是TBP DNA结合活性的有效抑制剂。此外，E7的这种活性在E7被CK2磷酸化后增加，这与其对TBP的亲和力增加一致。最后，一种在结合TBP能力上有缺陷的突变型E7蛋白，对TBP与DNA的结合没有影响。这些结果表明，E7 - TBP相互作用的一个后果是TBP DNA结合活性的丧失，这可能为E7的转录抑制作用提供一种解释。
