组蛋白不同乙酰化位点突变对酵母细胞生长和Ssa3、Gal1基因表达的影响

组蛋白乙酰化对基因表达和细胞生长非常重要.为揭示组蛋白H3K14和H4K8的乙酰化修饰对不同条件下细胞生长和Ssa3、Gal1基因表达的重要性及二者功能差异.构建了H3K14、H4K8分别突变为精氨酸的单突变株S14、S8及二者同时突变的双突变株D814,并对其在正常、高温、咖啡因存在等条件下生长及Ssa3、Gal1表达进行比较.结果表明,所有突变株对咖啡因敏感性增加;D814对温度敏感,且在供试条件下其生长及Ssa3和Gal1激活均明显慢于野生型和单突变株;除半乳糖和葡萄糖为单一碳源,30℃时两单突变株差别不大外,其它条件下S8生长及Ssa3和Gal1激活均慢于S14.表明H3K14、H4K8乙酰化对细胞生长和适应不利环境非常重要,而且在对不利条件的快速适应方面,H4K8的乙酰化修饰可能更为重要.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基因激活延迟所致.     

Transcriptional Activities of a Winged Bean Kunitz Chymotrypsin Inhibitor Gene Promoter in Stable and Transient Expression Systems

Sequential deletions of the promoter region of the WCI-3b gene, which encodes the major chymotrypsin inhibitor of winged bean, were constructed and their expression was analyzed in transgenic tobacco plants and in bombarded winged bean seeds. In transgenic tobacco plants, a critical promoter region which is important for high levels of expression in seeds was identified, but deletion of this region had essentially no effect when bombarded into winged bean seeds.     

The Role of Gcr1p in the Transcriptional Activation of Glycolytic Genes in Yeast Saccharomyces Cerevisiae

To study the interdependence of Gcr1p and Rap1p, we prepared a series of synthetic regulatory sequences that contained various numbers and combinations of CT-boxes (Gcr1p-binding sites) and RPG-boxes (Rap1p-binding sites). The ability of the synthetic oligonucleotides to function as regulatory sequences was tested using an ENO1-lacZ reporter gene. As observed previously, synthetic oligonucleotides containing both CT- and RPG-boxes conferred strong UAS activity. Likewise, a lone CT-box did not show any UAS activity. By contrast, oligonucleotides containing tandem CT-boxes but no RPG-box conferred strong promoter activity. This UAS activity was not dependent on position or orientation of the oligonucleotides in the 5'' noncoding region. However, it was dependent on both GCR1 and GCR2. These results suggest that the ability of Gcr1p to bind Gcr1p-binding sites in vivo is not absolutely dependent on Rap1p. Eleven independent mutants of GCR1 were isolated that conferred weak UAS activity to a single CT-box. Five mutants had single mutations in Gcr1p''s DNA-binding domain and displayed slightly higher affinity for the CT-box. These results support the hypothesis that Gcr1p and Gcr2p play the central role in glycolytic gene expression and that the function of Rap1p is to facilitate the binding of Gcr1p to its target.