Sánchez-Alonso P, Guzmán P
Departamento de Ingeniería Genética de Plantas, Centro de Investigación y de Estudios Avanzados del IPN, UNIDAD IRAPUATO, Gto., México.
Genetics. 1998 Mar;148(3):1043-54. doi: 10.1093/genetics/148.3.1043.
In this study we have established the structure of chromosome ends in the basidiomycete fungus Ustilago maydis. We isolated and characterized several clones containing telomeric regions and found that as in other organisms, they consist of middle repeated DNA sequences. Two principal types of sequence were found: UTASa was highly conserved in nucleotide sequence and located almost exclusively at the chromosome ends, and UTASb was less conserved in nucleotide sequence than UTASa and found not just at the ends but highly interspersed throughout the genome. Sequence analysis revealed that UTASa encodes an open reading frame containing helicase motifs with the strongest homology to RecQ helicases; these are DNA helicases whose function involves the maintenance of genome stability in Saccharomyces cerevisiae and in humans, and the suppression of illegitimate recombination in Escherichia coli. Both UTASa and UTASb contain a common region of about 300 bp located immediately adjacent to the telomere repeats that are also found interspersed in the genome. The analysis of the chromosome ends of U. maydis provides information on the general structure of chromosome ends in eukaryotes, and the putative RecQ helicase at UTASa may reveal a novel mechanism for the maintenance of chromosome stability.
在本研究中，我们确定了担子菌真菌玉米黑粉菌染色体末端的结构。我们分离并鉴定了几个包含端粒区域的克隆，发现与其他生物一样，它们由中度重复的DNA序列组成。发现了两种主要的序列类型：UTASa在核苷酸序列上高度保守，几乎只位于染色体末端；UTASb在核苷酸序列上比UTASa保守性低，不仅在末端发现，而且在整个基因组中高度散布。序列分析表明，UTASa编码一个开放阅读框，其中包含与RecQ解旋酶具有最强同源性的解旋酶基序；这些是DNA解旋酶，其功能涉及在酿酒酵母和人类中维持基因组稳定性，以及在大肠杆菌中抑制异常重组。UTASa和UTASb都包含一个约300 bp的共同区域，该区域紧邻端粒重复序列，在基因组中也呈散布状。对玉米黑粉菌染色体末端的分析提供了有关真核生物染色体末端一般结构的信息，并且UTASa处假定的RecQ解旋酶可能揭示了一种维持染色体稳定性的新机制。
