Differential Effects of Tra2ß Isoforms on HIV-1 RNA Processing and Expression

Abstract

Balanced processing of HIV-1 RNA is critical to virus replication and is regulated by host factors. In this report, we demonstrate that overexpression of either Tra2α or Tra2β results in a marked reduction in HIV-1 Gag/ Env expression, an effect associated with changes in HIV-1 RNA accumulation, altered viral splice site usage, and a block to export of HIV-1 genomic RNA. A natural isoform of Tra2β (Tra2ß3), lacking the N-terminal RS domain, also suppressed HIV-1 expression but had different effects on viral RNA processing. The functional differences between the Tra2β isoforms were also observed in the context of another RNA substrate indicating that these factors have distinct functions within the cell. Finally, we demonstrate that Tra2ß depletion results in a selective reduction in HIV-1 Env expression as well as an increase in multiply spliced viral RNA. Together, the findings indicate that Tra2α/β can play important roles in regulating HIV-1 RNA metabolism and expression.

An activator of G protein-coupled receptor and MEK1/2-ERK1/2 signaling inhibits HIV-1 replication by altering viral RNA processing

“…Although this compound has been described to weakly inhibit microsomal prostaglandin E synthase-1, the concentrations required to suppress HIV-1 gene expression (IC 50 : 700 nM-1.8 μM, Fig 1) is well below those required to inhibit this enzyme (50 μM for 71% reduction), supporting the hypothesis that 5342191 modulation of HIV-1 RNA accumulation (Fig 2B-2D) is a novel activity unrelated to its effect on this enzyme [67]. Consistent with this conclusion, treatment of cells with 5342191 altered the abundance/modification of a subset of SR proteins known to regulate HIV-1 RNA processing ( Fig 2K) [27,42,43,48,50,54,55,68]: increasing SRSF4 levels (abundance and modification) by 2.1 fold (to 210%) and decreasing SRSF1 and SRSF3 abundance by 2 fold and 30% (to 50% and 70%, resp.) relative to controls, without altering SRSF 6, 7, 9, and Tra2α levels.…”

Modulation of the splicing regulatory function of SRSF10 by a novel compound that impairs HIV-1 replication

“…Details of plasmids expressing 3XFlag-SRSF10, Flag-SRSF10 and HA-tagged SRSF10 were also previously described ( 31 ). Plasmid transfections in HeLa-HIV cells (HeLa rtTA-HIV-ΔMls cells as described in references 13 , 18 , 19 ) or 293 cells (EcR 293 cells from Thermo Fisher Scientific) were carried out with polyethyleneimide (Polysciences Inc.) or Lipofectamine 2000 (Invitrogen) according to the manufacturer's instructions.…”

“…In contrast to the results for IDC16, we identify the splicing regulatory protein SRSF10 as being affected by 1C8. Notably, treatment of cells with 1C8 promotes the dephosphorylation of SRSF10 and increases its interaction with hTra2β, a known regulator of HIV-1 splicing ( 18 , 19 ). Consistent with 1C8 targeting the activity of SRSF10 and hTra2β, we identify cellular alternative splicing events controlled by SRSF10 and hTra2β that are reactive to 1C8, but that require concentrations higher than those needed for HIV-1 inhibition.…”

Identification of small molecule modulators of HIV-1 Tat and Rev protein accumulation

“…Multiple host factors contribute to the regulation of HIV-1 RNA processing, many of which belong to the SR and hnRNP family of splicing regulators [ 1 ]. Both overexpression and depletion studies have highlighted several members of each family that play pivotal roles in regulating HIV-1 gene expression and virus replication [ 2 , 5 – 11 ]. More relevant to the goal of the development of therapeutics, several groups have identified small molecules (digoxin, chlorhexidine, IDC16, ABX464, 8-azaguanine, 5310150, 1C8) which appear to function at different stages of HIV-1 RNA processing/expression to block viral structural protein expression [ 12 – 17 ].…”