Nishida K, Suzuki S, Kimura Y, Nomura N, Fujie M, Yamada T
Department of Molecular Biotechnology, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima, Japan.
Virology. 1998 Mar 15;242(2):319-26. doi: 10.1006/viro.1998.9030.
More than 80 group I introns were detected and characterized in Chlorella viruses isolated from various locations in Japan; the overall average frequency of viruses containing the group I intron was 8.0%. Although most of these introns were inserted in the gene for either transcriptional elongation factor TFIIS (approximately 60%) or URF 14.2 (unidentified open reading frame coding for a 14.2-kDa polypeptide) (approximately 40%), in a few cases, the gene for the major capsid protein Vp52 contained an intron. These introns were biologically active (self-splicing) both in vivo and in vitro. Viruses that contained introns almost usually contained only one, but more than two introns coexisted in several virus isolates. Nucleotide sequence analysis showed that the intron sequences have diverged under strong constraint of the exon genes: introns in the same gene showed more than 99% sequence identity, whereas introns in different genes were only 72-78% identical. Phylogenetic analysis suggested relatedness of these introns to those found in the rRNA genes of a variety of organisms including green algae, red algae, red algae, yeasts, fungi, and protozoa.
在从日本各地分离出的小球藻病毒中检测并鉴定了80多个I组内含子；含有I组内含子的病毒的总体平均频率为8.0%。尽管这些内含子大多插入转录延伸因子TFIIS基因（约60%）或URF 14.2（编码14.2 kDa多肽的未鉴定开放阅读框）基因（约40%），但在少数情况下，主要衣壳蛋白Vp52基因含有一个内含子。这些内含子在体内和体外均具有生物活性（自我剪接）。含有内含子的病毒几乎通常只含有一个，但在几种病毒分离物中存在两个以上内含子共存的情况。核苷酸序列分析表明，内含子序列在外显子基因的强烈限制下发生了分化：同一基因中的内含子序列同一性超过99%，而不同基因中的内含子序列同一性仅为72-78%。系统发育分析表明，这些内含子与包括绿藻、红藻、酵母、真菌和原生动物在内的多种生物的rRNA基因中的内含子相关。
