酿酒酵母组蛋白H3 K4L和K36L突变对细胞生长和GAL1、SSA3、PHO5表达的影响

Effects of histone H3 K4L and K36L mutations on the cell growth and the transcription of GAL1, SSA3 and PHO5 in Saccharomyces cerevisiae

组蛋白甲基化和乙酰化修饰对基因表达和细胞生长至关重要,为揭示组蛋白H3第4、36位赖氨酸(K)修饰对酵母生长和诱导基因表达的重要性及两位点功能差异,文章构建了两位点单独或共同突变为亮氨酸(L)的组蛋白突变株S4、S36和D436,对其在正常、半乳糖为单一碳源、高温、高盐等条件下的生长及GAL1、SSA3和PHO5表达进行比较。结果显示:D436对高温最敏感,各突变株对咖啡因显著敏感;3个突变株在高温、高盐、6-AU、咖啡因存在时的生长及GAL1、SSA3和PHO5的激活均明显慢于野生型;S4在高温、高盐条件下生长及GAL1激活慢于S36。H3-K4和H3-K36的翻译后修饰对细胞生长和适应不利环境非常重要,在对高温等逆境快速适应上,K4比K36更重要,组蛋白突变株的表型缺陷是因该条件下细胞生存所必需的诱导基因表达延迟所致,同一位点突变对不同基因表达有不同影响。3个突变株的缺陷表型严格上应是相应位点突变导致组蛋白修饰模式改变所造成的综合影响。

Post-translational modifications of histones, such as acetylation and methylation, have a pivotal role in regu- lating gene expression and cell growth. To elucidate the different roles and importance of H3K4 and H3K36 modifications in expression of inducible genes such as Call, SSA3, PH05 and the growth of yeast cell, we constructed three different yeast mutant strains carrying mutations of lysine 4, 36, or both to leucine in the histone H3 tail. Real-time PCR and sensi-five assay under the conditions of high temperature, NaC1, caffeine, 6-AU, or other conditions were carried out to charac- terize the effects of these mutations on cell growth and transcription levels of GALl, SSA3 and PH05. The results showed that three histone methylation mutants exhibited more severe growth defects and slower activation of GALl, SSA3 and PH05 than those of wild type; H3K4L/H3K36L double mutant strain D436 has the most severe phenotype. H3K4L mutants $4 exhibited more severe defects than those of H3K36L $36 mutants, especially at high temperature and high NaCI stresses. These results show that H3K4L and H3K36L are important for the growth and survival of yeast in unfavorable conditions, and that different mutations have different effects on the expression of single inducible gene, whereas the same mutation has different effects on the activation of different inducible genes in vivo. The post-translational modification of H3K4 is more important than H3K36 on the adaptation to harsh condition for yeast cell. The growth defects of histone mutant strains might arise from the slow activation of inducible gene essential for survival at harsh conditions.