The Canonical XXXX 3 Gene Product pIE611 of @entity19 Cytomegalovirus Is Dispensable for Viral Replication, but Mediates Transcriptional and Post-transcriptional Regulation of Viral Gene Products.

@entity32 @entity1522 @entity19 @entity20589 @entity9829 @entity44
UNASSIGNED: Transcription of @entity19 cytomegalovirus ( @entity20589 ) @entity9829 ie1 and ie3 is controlled by the major @entity9829 promoter/enhancer (MIEP) and requires differential splicing. Based on complete loss of genome replication of an @entity20589 mutant carrying a deletion of the ie3-specific exon 5, the multifunctional IE3 protein (611 @entity1522 , pIE611) is considered essential for viral replication. Our analysis of ie3 transcription resulted in the identification of novel ie3 isoforms derived from alternatively spliced ie3 transcripts. Construction of an IE3-HA virus by insertion of an in-frame HA-epitope sequence allowed detection of the @entity19 isoforms in infected cells, verifying that the newly identified transcripts are coding for proteins. This prompted the construction of an @entity20589 mutant lacking ie611, but retaining the coding capacity for the newly identified isoforms ie453 and ie310. Using   ie611 @entity20589 , we demonstrate the dispensability of the canonical ie3 gene product pIE611 for viral replication. To determine the role of pIE611 for viral gene expression during @entity20589 infection in an unbiased global approach, we used label-free quantitative mass-spectrometry to delineate pIE611-dependent changes of the @entity20589 proteome. Interestingly, further analysis revealed transcriptional as well as post-transcriptional regulation of @entity20589 gene products by pIE611. IMPORTANCE: Cytomegaloviruses are pathogenic b-herpesviruses persisting in a lifelong latency from which reactivation can occur under conditions of immuno-suppression, immuno- @entity44 or @entity32 . The switch from latency to reactivation requires expression of @entity9829 genes. Therefore, understanding of @entity9829 gene regulation might add insights into viral pathogenesis. The @entity19 cytomegalovirus ( @entity20589 ) @entity9829 (ie) 3 protein (611 @entity1522 , pIE611) is considered essential for viral replication. The identification of novel protein isoforms derived from alternatively spliced ie3 transcripts prompted the construction of an @entity20589 mutant lacking ie611, but retaining the coding capacity for the newly identified isoforms ie453 and ie310. Using   ie611 @entity20589 , we demonstrate the dispensability of the canonical ie3 gene product pIE611 for viral replication and delineated pIE611-dependent changes of the @entity20589 proteome. Our findings have fundamental implications for the interpretation of earlier studies on 'pIE3' functions and highlight the complex orchestration of @entity20589 gene regulation.
