UC San Diego

Alternative splicing, an essential post-transcriptional mechanism, is a target for HIV. HIV employs this process to produce multiple viral proteins from a single mRNA. Vpr, an accessory viral protein, supports HIV infection by manipulating cellular activities - inducing G2/M arrest, promoting viral protein expression, regulating apoptosis and cytotoxicity. Previous proteomic studies demonstrated that Vpr modulates the activity of serine/arginine-rich specific kinases (SRPKs). SRPKs regulate splicing by phosphorylating serine and arginine-rich (SR) proteins and regulating their intracellular location. Thus, we hypothesized that Vpr influences alternative splicing by modulating SRPK phosphorylation directly or via a secondary effect of Vpr-induced G2/M arrest. We confirmed that Vpr enhances Env protein expression, then probed whether this could be due to Vpr-induced increases in Env mRNA. We examined the effects of Vpr on cellular splicing, first confirming that Vpr modulates SRPK1 phosphorylation, then employing the E1A splicing reporter assay to assess Vpr’s effects on SRPK-dependent splicing. We also evaluated whether the Vpr-dependent effects we saw were secondary to G2/M arrest triggered by Vpr or a result of other direct effects of Vpr. These findings lay the foundation for further studies of Vpr’s modulation of viral and cellular splicing