Department of Molecular Genetics, University of Toronto, Toronto, ON M5S1A8, Canada.
Nucleic Acids Res. 2012 Apr;40(8):3663-75. doi: 10.1093/nar/gkr1238. Epub 2011 Dec 19.
Control of RNA processing plays a major role in HIV-1 gene expression. To explore the role of several hnRNP proteins in this process, we carried out a siRNA screen to examine the effect of depletion of hnRNPs A1, A2, D, H, I and K on HIV-1 gene expression. While loss of hnRNPs H, I or K had little effect, depletion of A1 and A2 increased expression of viral structural proteins. In contrast, reduced hnRNP D expression decreased synthesis of HIV-1 Gag and Env. Loss of hnRNP D induced no changes in viral RNA abundance but reduced the accumulation of HIV-1 unspliced and singly spliced RNAs in the cytoplasm. Subsequent analyses determined that hnRNP D underwent relocalization to the cytoplasm upon HIV-1 infection and was associated with Gag protein. Screening of the four isoforms of hnRNP D determined that, upon overexpression, they had differential effects on HIV-1 Gag expression, p45 and p42 isoforms increased viral Gag synthesis while p40 and p37 suppressed it. The differential effect of hnRNP D isoforms on HIV-1 expression suggests that their relative abundance could contribute to the permissiveness of cell types to replicate the virus, a hypothesis subsequently confirmed by selective depletion of p45 and p42.
RNA 加工的控制在 HIV-1 基因表达中起着重要作用。为了探索几种 hnRNP 蛋白在这个过程中的作用，我们进行了 siRNA 筛选实验，以研究 hnRNPs A1、A2、D、H、I 和 K 的缺失对 HIV-1 基因表达的影响。虽然 hnRNPs H、I 或 K 的缺失几乎没有影响，但 A1 和 A2 的缺失增加了病毒结构蛋白的表达。相比之下，hnRNP D 的减少降低了 HIV-1 Gag 和 Env 的合成。hnRNP D 的缺失不会改变病毒 RNA 的丰度，但会减少 HIV-1 未剪接和单剪接 RNA 在细胞质中的积累。随后的分析确定，hnRNP D 在 HIV-1 感染后发生了向细胞质的重新定位，并与 Gag 蛋白相关。hnRNP D 的四个亚型的筛选表明，在过表达时，它们对 HIV-1 Gag 表达有不同的影响，p45 和 p42 亚型增加了病毒 Gag 的合成，而 p40 和 p37 则抑制了它。hnRNP D 亚型对 HIV-1 表达的差异影响表明，它们的相对丰度可能有助于细胞类型对病毒复制的允许性，这一假设随后通过选择性耗尽 p45 和 p42 得到了证实。
