Chen E J, Frand A R, Chitouras E, Kaiser C A
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Mol Cell Biol. 1998 Dec;18(12):7139-46. doi: 10.1128/MCB.18.12.7139.
Secretory proteins in eukaryotic cells are transported to the cell surface via the endoplasmic reticulum (ER) and the Golgi apparatus by membrane-bounded vesicles. We screened a collection of temperature-sensitive mutants of Saccharomyces cerevisiae for defects in ER-to-Golgi transport. Two of the genes identified in this screen were PRP2, which encodes a known pre-mRNA splicing factor, and RSE1, a novel gene that we show to be important for pre-mRNA splicing. Both prp2-13 and rse1-1 mutants accumulate the ER forms of invertase and the vacuolar protease CPY at restrictive temperature. The secretion defect in each mutant can be suppressed by increasing the amount of SAR1, which encodes a small GTPase essential for COPII vesicle formation from the ER, or by deleting the intron from the SAR1 gene. These data indicate that a failure to splice SAR1 pre-mRNA is the specific cause of the secretion defects in prp2-13 and rse1-1. Moreover, these data imply that Sar1p is a limiting component of the ER-to-Golgi transport machinery and suggest a way that secretory pathway function might be coordinated with the amount of gene expression in a cell.
真核细胞中的分泌蛋白通过膜结合囊泡经内质网（ER）和高尔基体运输至细胞表面。我们在酿酒酵母的温度敏感突变体库中筛选了内质网到高尔基体运输存在缺陷的突变体。在此筛选中鉴定出的两个基因是PRP2，其编码一种已知的前体mRNA剪接因子，以及RSE1，一个我们发现对前体mRNA剪接很重要的新基因。在限制温度下，prp2-13和rse1-1突变体均积累了转化酶的内质网形式和液泡蛋白酶CPY。每个突变体中的分泌缺陷可通过增加SAR1的量来抑制，SAR1编码一种对于从内质网形成COPII囊泡必不可少的小GTP酶，或者通过从SAR1基因中删除内含子来抑制。这些数据表明，未能剪接SAR1前体mRNA是prp2-13和rse1-1中分泌缺陷的具体原因。此外，这些数据意味着Sar1p是内质网到高尔基体运输机制的一个限制成分，并提示了一种分泌途径功能可能与细胞中基因表达量相协调的方式。
