A global analysis of viral mRNA biogenesis during infection with Adenovirus type 5 ; Globale Analyse viraler mRNA Biogenese während adenoviraler Infektion

During the late phase of infection with adenovirus, cellular protein synthesis is shut off, due to a translational block of host cell mRNAs. It has been documented that cellular mRNAs fail to accumulate in the cytoplasm despite continued nuclear synthesis and processing. In contrast, the viral late mRNAs are selectively exported to the cytoplasm via the cellular export receptor TAP/NXF1. Interestingly, the activity of an E3-ubiquitin ligase complex composed of the viral E1B-55K and E4 Orf6 proteins and cellular factors is required, indicating that ubiquitin-dependent proteasomal degradation of one or more proteins could contribute directly or indirectly to the regulation of mRNA export during the late phase of infection. So far, the identity of such substrates is not known, nor has the mechanism by which viral mRNA species are distinguished from their cellular counterparts for export to the cytoplasm been identified; although several different models have been proposed. In these study, we search for possible degradation candidates for the viral-formed ubiquitin ligase. Also, attempting to identify additional parameters that control the differential export of viral and cellular transcripts, we performed global transcriptome analyses (RNA-Seq) to monitor changes in the cytoplasmic accumulation of RNAs expressed from cellular and viral genes as a function of time after infection of A549 cells. In this study, none of the tested cellular proteins were found to be degraded during infection. Thus, the role of the viral E1B/Orf6/E3 ubiquitin ligase in the selective export of viral late mRNAs remains unanswered. During this evaluation, hnRNP M was found to be conjugated by SUMO-1 and SUMO-2. Higher forms of SUMO-2-modified hnRNP M are formed at late time points of infection, depending on the presence of the viral E1B-55K protein. Our results suggest that phosphorylated E1B-55K enhances production of this higher forms of SUMO-2 conjugated hnRNP M. It was also found that hnRNP M accumulates around the viral RCs at late ...