Role of the OB-fold of RNA helicase A in the synthesis of HIV-1 RNA.

RNA helicase A (RHA), a DExD/H protein, contains a stretch of repeated arginine and glycine-glycine (RGG) residues and an oligonucleotide/oligosaccharide-binding fold (OB-fold) at the C-terminus. RHA has been reported to function as a transcriptional cofactor. This study shows the role of RGG and OB-fold domains of RHA in the activation of transcription and splicing of HIV-1 RNA. RHA stimulates HIV-1 transcription by enhancing the occupancy of RNA polymerase II on the proviral DNA. Deletion of RGG or both RGG and OB-fold does not change the transcriptional activity of RHA, nor does the stability of viral RNA. However, deletion of both RGG and OB-fold rather than deletion of RGG only results in less production of multiply spliced 6D RNAs. The results suggest that the OB-fold is involved in modulating HIV-1 RNA splicing in the context of some HIV-1 strains while it is dispensable for the activation of HIV-1 transcription.