酿酒酵母一个新的基因簇转录多顺反子的snoRNA前体

核仁小分子RNA (snoRNA)是一类在真核生物核糖体生物合成过程中起重要作用的小分子RNA .通过计算机分析国际分子生物学数据库及实验的方法 ,在酿酒酵母 (Saccharomycescerevisiae)中发现和鉴定了一个新的snoRNA(Z8)及其特殊的基因组织 .Z8snoRNA基因位于酿酒酵母第 13号染色体上 ,是酵母snoRNA基因簇的第 1个基因 ,编码boxC/D类反义snoRNA .结构分析指出该snoRNA指导 2 5SrRNA中第 2 42 1位尿苷酸的 2′ O 核糖的甲基化 .用遗传学方法将该基因缺失后 ,其对应位点的甲基化被取消 ,但细胞的生长并未受到影响 .Z8snoRNA基因的上游 2 47位 ,有一UsnoRNA启动子保守元素 .RT PCR的结果证明 ,Z8与该基因簇中其他snoRNA(Z7和Z6)基因共同转录成一个多顺反子的snoRNA前体 ,然后再被加工成熟 ,这是一种新的snoRNA基因表达方式 .     

A novel snoRNA gene cluster in yeast is transcribed as polycistronic pre-snoRNAs

Small nueleolar RNAs (snoRNAs) play an important role in eukaryotic rRNA biogenesis. By combination of a computer search of EMBL database and experimental procedure, a novel snoRNA coding sequence (Z8) was screened out and characterized from yeast Saccharomyces cerevisiae genome. Z8 snoRNA gene codes a boxC/D antisonse snoRNA which guides, deduced from structure analysis, the 2'-O-ribose methylation at U_(2421) of 25S rRNA. After disruption of Z8 snoRNA gene, the methylation at corresponding site was abolished, but no growth delay was observed in various cultural temperatures. Z8 DNA is the first gene of a gene cluster consisting of three cognate snoRNA genes which are located on an intergenie region of chromosome ⅩⅢ. This gene cluster is co-transcribed as a pelycistronic precursor from a 247 bp U snoRNA gene promoter, followed by processing to release individual snoRNAs, representing a new expression pattern of snoRNA genes.