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Abstract
hnRNP A2 is a cellular protein that is important for nucleocytoplasmic and cytosolic trafficking of the HIV-1 genomic RNA. Both hnRNP A2’s interaction with HIV-1 RNA and its expression levels influence the activities of Rev in mediating nucleocytoplasmic export of the HIV-1 genomic RNA. While the lack of Rev expression during HIV-1 gene expression results in nuclear retention of HIV-1 genomic RNA, we show here by fluorescence in situ hybridization and fractionation studies that the genomic RNA translocates to the cytoplasm when hnRNP A2/B1 are depleted from cells. Polyribosome analyses revealed that the genomic RNA was shunted into a cytoplasmic, dense polyribosomal fraction. This fraction contained several RNA-binding proteins involved in viral gene expression and RNA trafficking but did not contain the translation initiation factor, eIF4G1. Amino acid incorporation into nascent polypeptides in this fraction was also greatly reduced, demonstrating that this fraction contains mRNAs that are poorly translated. These results demonstrate that hnRNP A2/B1 expression plays roles in the nuclear retention of the HIV-1 genomic RNA in the absence of Rev and in the release of the genomic RNA from translationally inactive, cytoplasmic RNP complexes.
Disclosure of Potential Conflicts of Interest
No potential conflicts of interest were disclosed.
Acknowledgments
We especially thank Dr Anne Monette, Melanie Halvorsen, and Martin Lehmann for contributions to experiments reported in this manuscript, Drs Benoit Chabôt, Nahum Sonenberg, Graciella Boccaccio for antibodies, Drs Sadaie, Hammarskjöld, Rekosh, and the AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH for reagents and Alan Cochrane for advice on the fractionation assay. AJM was supported by a Canadian Institutes of Health Research (CIHR) New Investigator Award and this work is supported by grants from the Canadian Foundation for AIDS Research and the CIHR (MOP-56974 & MOP-38111).
Supplemental Materials
Supplemental materials may be found here: www.landesbioscience.com/journals/rnabiology/article/26542