Jensen T H, Boulay J, Rosbash M, Libri D
Howard Hughes Medical Institute, Department of Biology, Brandeis University, Waltham, MA 02454, USA.
Curr Biol. 2001 Oct 30;11(21):1711-5. doi: 10.1016/s0960-9822(01)00529-2.
Nuclear mRNA metabolism relies on the interplay between transcription, processing, and nuclear export. RNA polymerase II transcripts experience major rearrangements within the nucleus, which include alterations in the structure of the mRNA precursors as well as the addition and perhaps even removal of proteins prior to transport across the nuclear membrane. Such mRNP-remodeling steps are thought to require the activity of RNA helicases/ATPases. One such protein, the DECD box RNA-dependent ATPase Sub2p/UAP56, is involved in both early and late steps of spliceosome assembly. Here, we report a more general function of Saccharomyces cerevisiae Sub2p in mRNA nuclear export. We observe a rapid and dramatic nuclear accumulation of poly(A)(+) RNA in strains carrying mutant alleles of sub2. Strikingly, an intronless transcript, HSP104, also accumulates in nuclei, suggesting that Sub2p function is not restricted to splicing events. The HSP104 transcripts are localized in a single nuclear focus that is suggested to be at or near their site of transcription. Intriguingly, Sub2p shows strong genetic and functional interactions with the RNA polymerase II-associated DNA/DNA:RNA helicase Rad3p as well as the nuclear RNA exosome component Rrp6p, which was independently implicated in the retention of mRNAs at transcription sites. Taken together, our data suggest that Sub2p functions at an early step in the mRNA export process.
核mRNA代谢依赖于转录、加工和核输出之间的相互作用。RNA聚合酶II转录本在细胞核内经历重大重排，这包括mRNA前体结构的改变以及在穿过核膜运输之前蛋白质的添加甚至可能去除。这种mRNP重塑步骤被认为需要RNA解旋酶/ATP酶的活性。一种这样的蛋白质，DECD框RNA依赖性ATP酶Sub2p/UAP56，参与剪接体组装的早期和晚期步骤。在这里，我们报道了酿酒酵母Sub2p在mRNA核输出中的更普遍功能。我们观察到在携带sub2突变等位基因的菌株中，poly(A)(+) RNA迅速且显著地在细胞核中积累。引人注目的是，一种无内含子转录本HSP104也在细胞核中积累，这表明Sub2p的功能不限于剪接事件。HSP104转录本定位在单个核焦点处，推测该焦点位于其转录位点或附近。有趣的是，Sub2p与RNA聚合酶II相关的DNA/DNA:RNA解旋酶Rad3p以及核RNA外泌体成分Rrp6p表现出强烈的遗传和功能相互作用，Rrp6p独立地参与了mRNA在转录位点的滞留。综上所述，我们的数据表明Sub2p在mRNA输出过程的早期发挥作用。
