Boucher H, Mercure S, Montplaisir S, Lemay G
Département de Microbiologie et Immunologie, Université de Montréal, Qué., Canada.
Gene. 1996 Nov 21;180(1-2):189-96. doi: 10.1016/s0378-1119(96)00453-2.
In the present study, we determined the sequence of group I self-splicing introns found in the large ribosomal RNA subunit of Candida albicans, Candida stellatoidea and the recently-described species Candida dubliniensis. It was found that both the intron and ribosomal RNA nucleotide sequences are almost perfectly identical between different C. albicans strains as well as between C. albicans and C. stellatoidea strains. Comparisons of ribosomal RNA sequences suggest that local isolates of atypical C. albicans from individuals infected with human immunodeficiency virus can be assigned to the C. dubliniensis species. C. dubliniensis strains also harbor a group I intron in their ribosomal RNA, as observed in about 40% of C. albicans strains and all C. stellatoidea strains. This novel C. dubliniensis group I intron is identical to the C. albicans and C. stellatoidea intron, except for two widely divergent stem-loop regions. Despite these differences, the C. dubliniensis intron possesses self-splicing ability in an in vitro assay. Taken together, these data support the idea that C. albicans and C. stellatoidea should be joined together as variants of the same species while C. dubliniensis is a distinct but closely related microorganism. To our knowledge, the C. albicans and C. dubliniensis introns are the first example of a pair of homologous group I introns differing only by the presence of apparently facultative sequences in some stem-loops suspected to be involved in stabilization of tertiary structure.
在本研究中，我们测定了白色念珠菌、星状念珠菌以及最近描述的都柏林念珠菌的大核糖体RNA亚基中发现的I组自我剪接内含子的序列。结果发现，不同白色念珠菌菌株之间以及白色念珠菌与星状念珠菌菌株之间，内含子和核糖体RNA核苷酸序列几乎完全相同。核糖体RNA序列比较表明，从感染人类免疫缺陷病毒的个体中分离出的非典型白色念珠菌局部菌株可归为都柏林念珠菌物种。都柏林念珠菌菌株在其核糖体RNA中也含有一个I组内含子，约40%的白色念珠菌菌株和所有星状念珠菌菌株中也观察到这一情况。这个新的都柏林念珠菌I组内含子与白色念珠菌和星状念珠菌的内含子相同，只是有两个差异很大的茎环区域。尽管存在这些差异，但都柏林念珠菌内含子在体外试验中具有自我剪接能力。综上所述，这些数据支持以下观点：白色念珠菌和星状念珠菌应作为同一物种的变体合并在一起，而都柏林念珠菌是一种独特但密切相关的微生物。据我们所知，白色念珠菌和都柏林念珠菌的内含子是一对同源I组内含子的首个例子，它们之间的差异仅在于某些茎环中存在明显的兼性序列，这些序列可能参与三级结构的稳定。
