Recombination-mediated lengthening of terminal telomeric repeats requires the Sgs1 DNA helicase
Recombination-mediated lengthening of terminal telomeric repeats requires the Sgs1 DNA helicase
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DOI：
10.1073/pnas.061579598
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发表时间：
2001-03-13
影响因子：
11.1
通讯作者：
Sinclair, DA
中科院分区：
文献类型：
--
作者：
Cohen, H;Sinclair, DA
酿酒酵母SGS 1基因编码RecQ样DNA解旋酶，其人类同源物与遗传不稳定性疾病、布卢姆综合征（BS）、罗斯蒙-汤姆森综合征（RTS）和沃纳综合征（WS）有关。端粒酶阴性的酵母细胞可以通过两种重组端粒延长途径从衰老中恢复。“I型”途径产生具有大的端粒和亚端粒序列块和短的末端重复序列的端粒。“II型”途径产生具有极长的异质末端重复序列的端粒，这让人想起在端粒酶缺陷的人类肿瘤和肿瘤衍生细胞系中观察到的长端粒。在这里，我们报告说，端粒酶阴性（est 2）酵母细胞缺乏SGS 1衰老更快，经历了更高的端粒侵蚀率，并推迟了一代的幸存者。产生的est 2 sgs 1幸存者生长不良，停滞在G（2）/M期，仅具有I型端粒，这意味着SGS 1对II型途径至关重要。小鼠WS基因抑制了est 2 sgs 1存活者的缓慢生长和G（2）/M停滞表型，这表明SGS 1的端粒功能是保守的。再引入SCS 1到EST 2 SGS 1幸存者恢复生长速率和延长终末束约300 bp。这两种表型绝对依赖于Sgs 1解旋酶活性。引入具有解旋酶活性的sgs 1羧基末端截短等位基因恢复了生长速率，而在大多数情况下没有延长端粒，表明II型端粒在没有端粒酶的情况下对于正常生长是不必要的。
The Saccharomyces cerevisiae SGS1 gene encodes a RecQ-like DNA helicase, human homologues of which are implicated in the genetic instability disorders, Bloom syndrome (BS), Rothmund-Thomson syndrome (RTS), and Werner syndrome (WS). Telomerase-negative yeast cells can recover from senescence via two recombinational telomere elongation pathways. The "type I" pathway generates telomeres with large blocks of telomeric and subtelomeric sequences and short terminal repeat tracts. The "type II" pathway generates telomeres with extremely long heterogeneous terminal repeat tracts, reminiscent of the long telomeres observed in telomerase-deficient human tumors and tumor-derived cell lines. Here, we report that telomerase-negative (est2) yeast cells lacking SGS1 senesced more rapidly, experienced a higher rate of telomere erosion, and were delayed in the generation of survivors. The est2 sgs1 survivors that were generated grew poorly, arrested in G(2)/M and possessed exclusively type I telomeres, implying that SGS1 is critical for the type II pathway. The mouse WS gene suppressed the slow growth and G(2)/M arrest phenotype of est2 sgs1 survivors, arguing that the telomeric function of SGS1 is conserved. Reintroduction of SCS1 into est2 sgs1 survivors restored growth rate and extended terminal tracts by approximate to 300 bp. Both phenotypes were absolutely dependent on Sgs1 helicase activity. Introduction of an sgs1 carboxyl-terminal truncation allele with helicase activity restored growth rate without extending telomeres in most Eases, demonstrating that type II telomeres are not necessary for normal growth in the absence of telomerase.