Department of Microbiology and Molecular Biology, College of Bioscience and Biotechnology, Chungnam National University, Daejeon 305-764, Korea.
Yeast. 2010 Jul;27(7):443-52. doi: 10.1002/yea.1762.
In the yeast Saccharomyces cerevisiae, the unfolded protein response (UPR) involves the unconventional splicing of HAC1 mRNA, which is mediated by the activated Ire1p transmembrane kinase/endonuclease. In this study, we isolated and characterized a Yarrowia lipolytica HAC1 (YlHAC1) encoding a basic-leucine zipper transcription factor. The null mutant strain of YlHAC1 (DeltaYlhac1) displayed a significantly increased sensitivity to dithiothreitol (DTT) and tunicamycin (TM), along with a defect in hyphal growth, suggesting the essential function of YlHAC1 in UPR. The unconventional splicing of YlHAC1 mRNA occurred under the UPR conditions induced by DTT or TM treatment. Unlike S. cerevisiae HAC1 mRNA with an intron of 252 nt, YlHAC1 mRNA was shown to harbour a short intron of length 29 nt. The YlHAC1 mRNA harboured the nucleotides CAG, conserved at the intron borders in the filamentous fungi hac1/hacA and mammalian XBP1, as well as a conserved bipartite element within the 3' untranslated region. The expression of the spliced form of YlHAC1 mRNA in the wild-type andDeltaYlhac1 strains resulted in an increased resistance to DTT, thereby indicating that the spliced form is translated into a functional YlHac1p.
在酵母酿酒酵母中，未折叠蛋白反应（UPR）涉及 HAC1 mRNA 的非常规剪接，该剪接由激活的 Ire1p 跨膜激酶/内切酶介导。在这项研究中，我们分离并鉴定了一种假丝酵母 HAC1（YlHAC1），它编码一种碱性亮氨酸拉链转录因子。YlHAC1 的 null 突变株（DeltaYlhac1）对二硫苏糖醇（DTT）和衣霉素（TM）表现出明显的敏感性增加，并且菌丝生长缺陷，表明 YlHAC1 在 UPR 中具有重要功能。在 DTT 或 TM 处理诱导的 UPR 条件下，发生了 YlHAC1 mRNA 的非常规剪接。与含有 252 个核苷酸的内含子的 S. cerevisiae HAC1 mRNA 不同，YlHAC1 mRNA 含有 29 个核苷酸的短内含子。YlHAC1 mRNA 含有核苷酸 CAG，在丝状真菌 hac1/hacA 和哺乳动物 XBP1 的内含子边界保守，以及在 3'非翻译区的保守二部分元件。在野生型和 DeltaYlhac1 菌株中，剪接形式的 YlHAC1 mRNA 的表达导致对 DTT 的抗性增加，从而表明剪接形式被翻译为功能性 YlHac1p。
