Iwaguchi Shin-Ichi, Suzuki Mina, Sakai Naomi, Yokoyama Koji, Suzuki Takahito
Department of Biological Science, Nara Women's University, Nara, Japan.
Med Mycol. 2008 Nov;46(7):655-63. doi: 10.1080/13693780801989783.
Clinical isolates of the medically important fungus Candida albicans show electrophoretic karyotype variations. Chromosome translocation is considered to be one of the possible mechanisms of karyotype variation and has been shown to occur very frequently at or near the unique repeated DNA sequences which comprise the Major Repeat Sequence (MRS) on the genome. The MRS consists of the repeated sequences RB2, RPS, and HOK. We previously showed the insertion at the RB2 region might initiate chromosome translocation in strain STN22u2 of C. albicans. To ask whether the insertion of a URA cassette into the RB2 but not into RPS and HOK causes chromosome translocation in C. albicans strains, we transformed three URA cassettes into strain CAI-4, which is commonly used as a host strain for gene knockout experiments. We found chromosome rearrangements followed the insertion of URA cassettes into RB2 in strain CAI-4. Three transformants had an extra chromosome showing the loss of the 7A and 7C region from one chromosome 7 homologue. The recombination occurred at or after the insertion of URA cassette into RB2. Insertion there seems to cause chromosome rearrangement and thus RB2 is considered one of the important elements for initiation of chromosome rearrangement.
医学上重要的真菌白色念珠菌的临床分离株表现出电泳核型变异。染色体易位被认为是核型变异的可能机制之一，并且已证明在基因组中构成主要重复序列（MRS）的独特重复DNA序列处或其附近非常频繁地发生。MRS由重复序列RB2、RPS和HOK组成。我们之前表明，在RB2区域的插入可能会引发白色念珠菌STN22u2菌株中的染色体易位。为了探究将URA盒插入RB2而非RPS和HOK是否会导致白色念珠菌菌株中的染色体易位，我们将三个URA盒转化到菌株CAI-4中，该菌株通常用作基因敲除实验的宿主菌株。我们发现，在菌株CAI-4中，将URA盒插入RB2后会发生染色体重排。三个转化体有一条额外的染色体，显示出一条7号染色体同源物上的7A和7C区域缺失。重组发生在URA盒插入RB2时或之后。在那里的插入似乎会导致染色体重排，因此RB2被认为是染色体重排起始的重要元件之一。
