Suppression of HIV-1 Nef translation by Sam68 mutant-induced stress granules and nef mRNA sequestration (Mol Cell, 2009, 33:87-96)

報告日期: 2009/03/10
報告時間: 16:00/16:50
報告學生: 鄭 烈
講評老師: 張 堯
附件下載:

http://basicmed.med.ncku.edu.tw/admin/up_img/980310-2.pdf

Suppression of HIV-1 Nef Translation by Sam68 Mutant-Induced Stress Granules and nef mRNA Sequestration

Jorge Henao-Mejia, Ying Liu, In-Woo Park, Jizhong Zhang, Jeremy Sanford, and Johnny J. He

Molecular cell. 2009. 33: 87-96

 

Presenter: Lie Cheng

Commentator: Yao Chang Ph.D.

Presentation date: Mar 10, 2009.

Room 602 of medical college.

 

Abstract:

HIV Nef is an accessory protein crucial for HIV pathogenesis and AIDS disease progression. Previous evidence suggested that Nef is translated form the compeletely spliced viral pre-mRNA which is inherently regulated in the nucleus at the levels of pre-mRNA transcription, splicing and Rev-independent exporting. However, little is known about the cytoplasmic translational control on the expression of the HIV mRNAs, including the nef mRNA. Emerging evidence has indicates that the Sam68, an indispensable cellular factor for HIV Rev nuclear export function, is involved in the cytoplasmic processes of the HIV life cycle, because a dominant negative Sam68 nuclear localization signal (NLS) deletion mutant (410) inhibits HIV-1 replication without preventing constitutive Sam68 from entering the nucleus. Therefore, the authors test further whether Sam68410 may affect the cytoplasmic fate of the Nef mRNA, as the mechanism is critical for the intervention of HIV replication. By employing the NL4-3.Luc(env) and NL4-3.Luc(nef) luciferase reporter virus plasmid, the authors demonstrate that the expression of HIV Nef was suppressed by the existence of Sam68410. By confocal imaging analysis, the Sam68 410 was found to induce the formation of a granule-like structure in COS-7 and 293T cells. These granule-like structures were identified to be stress granules with colocalized Sam68 410, suggesting that the stress granule formation may contribute to the Sam68 410 mediated Nef suppression. In addition, By employing minigene constructs with HIV UTR regulator structures and the yeast three-hybrid assay, the authors demonstrated the specific interaction of Sam68 410 and the 3’UTR of Nef mRNA to the suppression of Nef expression. Most importantly, through the suppression of Nef expression, the Sam68 410 was able to functional restore the Nef mediated down regulation of membrane CD4 and MHC I molecules on HIV infected T lymphocytes and PBMCs. Taken together, these results validate the finding that Sam68 410 suppresses HIV-1 Nef expression through stress granule formation and support the possible translation of this finding into anti-HIV therapeutic development.

 

Reference:

Reddy, T.R., Xu, W., Mau, J.K., Goodwin, C.D., Suhasini, M., Tang, H., Frimpong, K., Rose, D.W., and Wong-Staal, F. (1999). Inhibition of HIV replication by dominant negative mutants of Sam68, a functional homolog of HIV-1 Rev. Nat. Med. 5, 635–642