Influence of viral immediate early proteins on AF4-complex dependent transcriptional processes

我们已经揭示了人AF 4多蛋白复合物的组成和功能（贝内迪克特，2011）。这种核复合物的分子量约为2 MDa，由至少13种蛋白质组成。该复合物的功能是激活RNA聚合酶II（RPII）以进行转录延伸。这是通过复合物结合的P-TEFb复合物完成的，该复合物使RPII的C-末端结构域（CTD）在丝氨酸-2残基处磷酸化。相关的组蛋白甲基转移酶CARM 1、NSD 1和DOT 1 L随后在组蛋白H3的不同残基处修饰染色质，沿着转录延伸过程（R2、R17、R26、K36、K79）。对于RPII活化的每个循环，AF 4复合物通过蛋白酶体途径被破坏。相比之下，AF 4 k.o.细胞几乎不能进行转录过程，因为倍增时间显著延长至18-21天。这表明AF 4复合物是转录过程的关键组分。在这里，我们要调查的现象，我们在我们的实验中观察到：病毒立即早期蛋白（IEP的）增强AF 4依赖的转录延长，并导致保护AF 4复合物对蛋白酶体降解。然而，增加量的AF 4蛋白不仅增强转录过程，而且对哺乳动物细胞表现出“转化”性质。出于这个原因，我们想要研究常见DNA病毒的病毒IEP如何改变人类AF 4复合物的组成，这些蛋白质复合物如何抵抗细胞降解以及这些病毒诱导的变化导致的致癌后果。

We have unravelled the composition and function of the human AF4 multiprotein complex (Benedikt, 2011). This nuclear complex has a molecular weight of ~2 MDa and is composed of at least 13 proteins. The function of this complex is to activate RNA Polymerase II (RPII) for transcriptional elongation. This is being done by the complex-bound P-TEFb complex which phosphorylates the C-terminal domain (CTD) of RPII at serine-2 residues. The associated histone methlytransferases, CARM1, NSD1 and DOT1L, are subsequently modifying the chromatin at distinct residues of histone H3 along with the process of transcriptional elongation (R2, R17, R26, K36, K79). For each cycle of RPII activation the AF4 complex becomes destructed via the proteasomal pathway. By contrast, AF4 k.o. cells are nearly unable to perform transcriptional processes, because doubling-times are dramatically extended up to 18-21 days. This suggests that the AF4 complex is a key component for the transcription process. Here, we want to investigate a phenomenon that we observed in our experiments: viral immediate early proteins (IEP's) enhance AF4-dependent transcriptional elongation and cause a protection of the AF4 complex against proteasomal degradation. However, increased amounts of AF4 protein does not only enhance transcriptional processes but also exhibit "transforming" properties for mammalian cells. For this reason we want to investigate how viral IEP's of common DNA viruses change the composition of the human AF4 complex, how these protein complexes become resistant against cellular degradation and which oncogenic consequences are resulting from these virus-induced changes.