CGI121 新发现的端粒酶调节因子
端粒是染色体末端的DNA重复序列，能够保持染色体的完整性。细胞每分裂一次，端粒就短一点。一旦端粒消耗殆尽，染色体则易于突变而导致动脉硬化和某些癌症。因此，端粒和细胞老化有明显的关系。 
telomere capping (1)
telomere capping ( 2)
在3月23日的Cell杂志上，来自加拿大和英国的研究人员确定出了与端粒覆盖染色体末端过程（telomere capping）有关的新基因。研究人员对酿酒酵母的整个基因组进行了筛选分析，以找出cdc13-1的抑制因子。Cdc13-1是telomere-capping蛋白Cdc13的等位基因。
研究人员确定出了5个新的抑制剂，其中包括之前未发现的基因YML036W——研究人员将其命名位CGI121。Cgi121是一种保守的蛋白质复合体（KEOPS复合体）的一部分。这种蛋白复合体包含蛋白激酶Bud32（被认为是肽酶Kael）和蛋白质Gon7。CGI121的删除会抑制cdc13-1：通过明显减少在cdc13-1 cgi121突变中积累的ssDNA水平来起到抑制作用。
BUD32或其他KEOPS成分的删除会导致端粒变短，并且无法将端粒加到DNA双链缺口上。
这些发现揭示出KEOPS复合体端粒的拆开和端粒的延长。
英文摘要
Telomere capping is the essential function of telomeres. To identify new genes involved in telomere capping, we carried out a genome-wide screen in Saccharomyces cerevisiae for suppressors of cdc13-1, an allele of the telomere-capping protein Cdc13. We report the identification of five novel suppressors, including the previously uncharacterized gene YML036W, which we name CGI121. Cgi121 is part of a conserved protein complex-the KEOPS complex-containing the protein kinase Bud32, the putative peptidase Kae1, and the uncharacterized protein Gon7. Deletion of CGI121 suppresses cdc13-1 via the dramatic reduction in ssDNA levels that accumulate in cdc13-1 cgi121 mutants. Deletion of BUD32 or other KEOPS components leads to short telomeres and a failure to add telomeres de novo to DNA double-strand breaks. Our results therefore indicate that the KEOPS complex promotes both telomere uncapping and telomere elongation.
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