Domsic Jeffrey K, Wang Yibin, Mayeda Akila, Krainer Adrian R, Stoltzfus C Martin
Program in Molecular Biology, University of Iowa, Iowa City, Iowa 52242, USA.
Mol Cell Biol. 2003 Dec;23(23):8762-72. doi: 10.1128/MCB.23.23.8762-8772.2003.
Human immunodeficiency virus type 1 (HIV-1) exonic splicing silencers (ESSs) inhibit production of certain spliced viral RNAs by repressing alternative splicing of the viral precursor RNA. Several HIV-1 ESSs interfere with spliceosome assembly by binding cellular hnRNP A/B proteins. Here, we have further characterized the mechanism of splicing repression using a representative HIV-1 hnRNP A/B-dependent ESS, ESSV, which regulates splicing at the vpr 3' splice site. We show that hnRNP A/B proteins bound to ESSV are necessary to inhibit E complex assembly by competing with the binding of U2AF65 to the polypyrimidine tracts of repressed 3' splice sites. We further show evidence suggesting that U1 snRNP binds the 5' splice site despite an almost complete block of splicing by ESSV. Possible splicing-independent functions of U1 snRNP-5' splice site interactions during virus replication are discussed.
1型人类免疫缺陷病毒（HIV-1）外显子剪接沉默子（ESSs）通过抑制病毒前体RNA的可变剪接来抑制某些剪接后病毒RNA的产生。几种HIV-1 ESSs通过结合细胞内的hnRNP A/B蛋白来干扰剪接体组装。在此，我们使用具有代表性的依赖HIV-1 hnRNP A/B的ESS（ESSV）进一步表征了剪接抑制机制，ESSV在vpr 3'剪接位点调节剪接。我们表明，与ESSV结合的hnRNP A/B蛋白通过与U2AF65结合到受抑制的3'剪接位点的多嘧啶序列竞争，对于抑制E复合物组装是必需的。我们进一步展示了证据，表明尽管ESSV几乎完全阻断了剪接，U1 snRNP仍结合5'剪接位点。讨论了病毒复制过程中U1 snRNP-5'剪接位点相互作用可能的非剪接依赖性功能。
