Genetic redundancy between SPT23 and MGA2: regulators of Ty-induced mutations and Ty1 transcription in Saccharomyces cerevisiae
Genetic redundancy between SPT23 and MGA2: regulators of Ty-induced mutations and Ty1 transcription in Saccharomyces cerevisiae
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DOI：
10.1128/mcb.17.8.4718
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发表时间：
1997-08
影响因子：
5.3
通讯作者：
S. Zhang;T. Burkett;I. Yamashita;D. Garfinkel
中科院分区：
文献类型：
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作者：
S. Zhang;T. Burkett;I. Yamashita;D. Garfinkel
SPT23是一种剂量依赖性的酿酒酵母ty诱导突变抑制因子。SPT23与MGA2具有相当的序列同源性，MGA2被鉴定为snf2施加的STA1转录阻滞的剂量依赖性抑制基因。虽然这些基因中的任何一个的单突变对细胞生长只有适度的影响，但spt23mga2双突变是不可存活的。与SPT23不同，截断形式的MGA2的多拷贝表达抑制了ty诱导突变的一小部分。SPT23/MGA2和SNF/SWI基因以相似的方式影响某些靶基因的转录。Spt23p似乎是HIS4 -912delta功能性HIS4表达所需的限速成分，HIS4 -912delta是由Ty1-912长末端重复序列诱导的启动子插入突变。此外，Spt23p和Mga2p都可以在融合到Gal4p dna结合域时激活转录，正如之前在Snf2p和Snf5p中观察到的那样。预测的Spt23p蛋白的N端有一个50个氨基酸的区域，这是反激活和抑制ty1诱导的突变和Spt23p的基本功能所必需的。细胞分离和细胞学实验表明Spt23p与细胞核有关。我们的研究结果表明，SPT23/MGA2可能通过改变染色质可及性来影响酵母中一个基因子集的转录。
SPT23 was isolated as a dosage-dependent suppressor of Ty-induced mutations in Saccharomyces cerevisiae. SPT23 shows considerable sequence homology with MGA2, a gene identified as a dosage-dependent suppressor of a snf2-imposed block on STA1 transcription in S. cerevisiae var. diastaticus. Although single mutations in either of these genes have only modest effects on cell growth, spt23 mga2 double mutants are inviable. Unlike SPT23, multicopy expression of a truncated form of MGA2 suppresses a narrow subset of Ty-induced mutations. SPT23/MGA2 and the SNF/SWI genes affect transcription of certain target genes in similar ways. Spt23p appears to be a rate-limiting component required for functional HIS4 expression of his4-912delta, a promoter insertion mutation induced by the Ty1-912 long terminal repeat. Furthermore, both Spt23p and Mga2p can activate transcription when fused to the Gal4p DNA-binding domain, as previously observed with Snf2p and Snf5p. A 50-amino-acid region in the N terminus of the predicted Spt23p protein is necessary and sufficient for the transactivation and necessary for suppression of Ty1-induced mutations and the essential function of Spt23p. Cell fractionation and cytological experiments suggest that Spt23p is associated with the nucleus. Our results suggest that SPT23/MGA2 affects transcription of a subset of genes in yeast, perhaps by changing chromatin accessibility.