Background
RNA helicase A (RHA), a DExH box protein, promotes annealing of tRNALys3, a primer for reverse transcription, to HIV-1 RNA and assembles into virus particles. A-kinase anchoring protein 95-like protein (HAP95) is a binding partner of RHA. The role of HAP95 in the annealing of tRNALys3 was examined in this study.
Conclusion
The results support a hypothesis that HAP95 may transiently block RHA's activity to protect the annealed tRNALys3 on viral RNA in the cells from removing by RHA during the packaging of RHA into virus particles, thus facilitating the annealing of tRNALys3 to HIV-1 RNA.
Results
HAP95 associates with the reverse transcriptase region of Pol protein of HIV-1. Decreasing endogenous HAP95 in HIV-1-producing 293T cells by siRNA reduces the amount of tRNALys3 annealed on viral RNA. This defect was further deteriorated by knockdown of RHA in the same cells, suggesting a cooperative effect between these two proteins. Biochemical assay in vitro using purified GST-tagged HAP95 shows that HAP95 may inhibit the activity of RHA.