Formation of functional centromeric chromatin is specified epigenetically in Candida albicans
Formation of functional centromeric chromatin is specified epigenetically in Candida albicans
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DOI：
10.1073/pnas.0606958103
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发表时间：
2006-10-03
影响因子：
11.1
通讯作者：
Carbon, John
中科院分区：
文献类型：
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作者：
Baum, Mary;Sanyal, Kaustuv;Carbon, John
在致病酵母白色念珠菌中，8条染色体的3-kb着丝粒DNA区域(CEN)具有不同和唯一的DNA序列。着丝粒的组蛋白CaCse4p(CENP-A同源)只出现在这些3kb的CEN区域内，形成专门的着丝粒染色质。通过将天然染色体与含有端粒和可选择标记的线性DNA片段进行同源重组，在体内获得的小染色体片段上保持着丝粒活性。体内获得的一条85kb的截短染色体，包括位于7号染色体69kb上的3kb CEN7基因座，在有丝分裂中稳定而自主地保持着，表明先前存在的活性CEN染色质在许多世代中仍然具有功能。同样的85kb的染色体片段，从白色念珠菌中分离出来的裸露DNA(不含染色质蛋白)，通过标准的DNA转化技术重新引入到白色念珠菌细胞中，无法改变功能性的CEN染色质，并且有丝分裂不稳定。微球菌核酸酶消化活性和非活性CEN染色质的比较表明，在活性着丝粒处周期性核小体阵列被破坏。染色质免疫沉淀和抗CaCse4p抗体证实，CEN7以裸露DNA的形式导入白色念珠菌细胞中，不会招募CaCse4p，也不会导致其扩散到距离活性CEN7染色质仅7kb的重复区域。这些结果表明，CaCse4p的募集和着丝粒的激活在白念珠菌中是表观遗传的，并保持不变。
In the pathogenic yeast Candida albicans, the 3-kb centromeric DNA regions (CEN) of each of the eight chromosomes have different and unique DNA sequences. The centromeric histone CaCse4p (CENP-A homolog) occurs only within these 3-kb CEN regions to form specialized centromeric chromatin. Centromere activity was maintained on small chromosome fragments derived in vivo by homologous recombination of a native chromosome with linear DNA fragments containing a telomere and a selectable marker. An in vivo derived 85-kb truncated chromosome containing the 3-kb CEN7 locus on 69 kb of chromosome 7 DNA was stably and autonomously maintained in mitosis, indicating that preexisting active CEN chromatin remains functional through many generations. This same 85-kb chromosome fragment, isolated as naked DNA (devoid of chromatin proteins) from C. albicans and reintroduced back into C albicans cells by standard DNA transformation techniques, was unable to reform functional CEN chromatin and was mitotically unstable. Comparison of active and inactive CEN chromatin digested with micrococcal nuclease revealed that periodic nucleosome arrays are disrupted at active centromeres. Chromatin immunoprecipitation with antibodies against CaCse4p confirmed that CEN7 introduced into C. albicans cells as naked DNA did not recruit CaCse4p or induce its spread to a duplicate region only 7 kb away from active CEN7 chromatin. These results indicate that CaCse4p recruitment and centromere activation are epigenetically specified and maintained in C. albicans.