Homologous recombination in Candida albicans:: role of CaRad52p in DNA repair, integration of linear DNA fragments and telomere length
Homologous recombination in Candida albicans:: role of CaRad52p in DNA repair, integration of linear DNA fragments and telomere length
复制标题
DOI：
10.1111/j.1365-2958.2004.04197.x
复制
发表时间：
2004-08-01
影响因子：
3.6
通讯作者：
Larriba, G
中科院分区：
文献类型：
--
作者：
Ciudad, T;Andaluz, E;Larriba, G
染色体重排在白念珠菌临床分离株和自发突变株中都很常见。看来，许多这些重排是由易位周围的主要序列重复（MSR），是存在于除3号染色体的所有染色体，这表明同源重组（HR）可能在这种生物体的生存发挥重要作用。为了获得关于这些过程的信息，我们克隆了RAD 52的同源物，其在酿酒酵母中是所有HR事件所需的唯一基因。CaRAD 52与S.啤酒。通过两个等位基因的顺序缺失构建了两个无效的Carad 52 Delta/Carad 52 Delta突变体，并通过基因的重组获得了两个重组菌株。这些突变体的表征表明，HR在修复由紫外线和拟辐射化合物甲基甲烷磺酸盐（MMS）引起的DNA损伤中起着至关重要的作用，而非同源末端连接途径（NHEJ）仅在不存在Rad 52 p或广泛的DNA损伤后使用。HR修复在指数生长的细胞中比在静止期细胞中更有效，可能是因为大量细胞处于细胞周期的晚期S或G（2）期（因此，可以使用姐妹染色单体作为重组修复的底物），而静止期细胞主要处于G（0）或G（1），只能使用染色体同源物进行修复。此外，CaRad 52 p是整合具有长侧翼同源序列的线性DNA所绝对需要的。最后，CaRad 52 p的缺失导致端粒的延长，即使在存在活性端粒酶的情况下也是如此，这是在任何其他生物体中都没有描述过的观察结果。这就提出了端粒酶和同源重组可能同时在C.白色念珠菌端粒。
Chromosomal rearrangements are common in both clinical isolates and spontaneous mutants of Candida albicans. It appears that many of these rearrangements are caused by translocations around the major sequence repeat (MSR) that is present in all chromosomes except chromosome 3, suggesting that homologous recombination (HR) may play an important role in the survival of this organism. In order to gain information on these processes, we have cloned the homologue of RAD52, which in Saccharomyces cerevisiae is the only gene required for all HR events. CaRAD52 complemented poorly a rad52 mutant of S. cerevisiae. Two null Carad52Delta/Carad52Delta mutants were constructed by sequential deletion of both alleles and two reconstituted strains were obtained by reintegration of the gene. Characterization of these mutants indicated that HR plays an essential role in the repair of DNA lesions caused by both UV light and the radiomimetic compound methyl-methane-sulphonate (MMS), whereas the non-homologous end-joining pathway (NHEJ) is used only in the absence of Rad52p or after extensive DNA damage. Repair by HR is more efficient in exponentially growing than in stationary cells, probably because a larger number of cells are in late S or G(2) phases of the cell cycle (and therefore, can use a sister chromatid as a substrate for recombinational repair), whereas stationary phase cells are mainly in G(0) or G(1), and only can be repaired using the chromosomal homologue. In addition, CaRad52p is absolutely required for the integration of linear DNA with long flanking homologous sequences. Finally, the absence of CaRad52p results in the lengthening of telomeres, even in the presence of an active telomerase, an observation not described in any other organism. This raises the possibility that both telomerase and homologous recombination may function simultaneously at C. albicans telomeres.