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

点击翻译按钮获取中文摘要

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.