Galy Vincent, Gadal Olivier, Fromont-Racine Micheline, Romano Alper, Jacquier Alain, Nehrbass Ulf
Unité de Biologie Cellulaire du Noyau, CNRS URA 2582, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France.
Cell. 2004 Jan 9;116(1):63-73. doi: 10.1016/s0092-8674(03)01026-2.
The molecular mechanism underlying the retention of intron-containing mRNAs in the nucleus is not understood. Here, we show that retention of intron-containing mRNAs in yeast is mediated by perinuclearly located Mlp1. Deletion of MLP1 impairs retention while having no effect on mRNA splicing. The Mlp1-dependent leakage of intron-containing RNAs is increased in presence of ts-prp18 delta, a splicing mutant. When overall pre-mRNA levels are increased by deletion of RRP6, a nuclear exosome component, MLP1 deletion augments leakage of only the intron-containing portion of mRNAs. Our data suggest, moreover, that Mlp1-dependent retention is mediated via the 5' splice site. Intriguingly, we found Mlp-proteins to be present only on sections of the NE adjacent to chromatin. We propose that at this confined site the perinuclear Mlp1 implements a quality control step prior to export, physically retaining faulty pre-mRNAs.
细胞核中含内含子的mRNA滞留的分子机制尚不清楚。在这里，我们表明酵母中含内含子的mRNA的滞留是由位于核周的Mlp1介导的。删除MLP1会损害滞留，而对mRNA剪接没有影响。在剪接突变体ts-prp18 delta存在的情况下，含内含子RNA的Mlp1依赖性泄漏增加。当通过删除核外体成分RRP6来增加整体前体mRNA水平时，删除MLP1仅增加mRNA内含子部分的泄漏。此外，我们的数据表明，Mlp1依赖性滞留是通过5'剪接位点介导的。有趣的是，我们发现Mlp蛋白仅存在于与染色质相邻的核膜部分。我们提出，在这个受限位点，核周的Mlp1在输出之前实施质量控制步骤，物理上保留有缺陷的前体mRNA。
