Cdc13 both positively and negatively regulates telomere replication
Cdc13 both positively and negatively regulates telomere replication
复制标题
DOI：
10.1101/gad.861001
复制
发表时间：
2001-02-15
影响因子：
10.5
通讯作者：
Lundblad, V
中科院分区：
文献类型：
--
作者：
Chandra, A;Hughes, TR;Lundblad, V
Cdc13是一种单链端粒dna结合蛋白，通过Cdc13上被Cdc13 -2突变消除的位点将端粒酶募集到染色体末端，从而积极调节酵母端粒复制。通过对一个新的突变Cdc13 -5的分析，我们发现Cdc13在端粒复制的负调控中具有单独的作用，这第二种调控活性的丧失导致端粒酶广泛延长端粒的G链，同时降低了协调C链合成的能力。CDC13 -5突变和DNA聚合酶α突变（也表现出端粒延长）被CDC13相互作用蛋白Stn1的表达增加所抑制，表明Stn1协调了后链复制复合体的作用与CDC13的调节活性。然而，Cdc13和Stn1之间的关联被Cdc13 -2所消除，同样的突变消除了Cdc13和端粒酶之间的相互作用。我们提出，由于端粒酶和负调节因子Stn1连续结合到Cdc13上的重叠位点，Cdc13参与了两个调控步骤——首先是阳性，然后是阴性。因此，Cdc13协调端粒两端的合成，首先招募端粒酶，随后限制端粒酶在响应c链复制时合成g链。
Cdc13 is a single-strand telomeric DNA-binding protein that positively regulates yeast telomere replication by recruiting telomerase to chromosome termini through a site on Cdc13 that is eliminated by the cdc13-2 mutation. Here we show that Cdc13 has a separate role in negative regulation of telomere replication, based on analysis of a new mutation, cdc13-5, Loss of this second regulatory activity results in extensive elongation of the G strand of the telomere by telomerase, accompanied by a reduced ability to coordinate synthesis of the C strand. Bath the cdc13-5 mutation and DNA polymerase alpha mutations (which also exhibit elongated telomeres) are suppressed by increased expression of the Cdc13-interacting protein Stn1, indicating that Stn1 coordinates action of the lagging strand replication complex with the regulatory activity of CDC13. However, the association between Cdc13 and Stn1 is abolished by cdc13-2, the same mutation that eliminates the interaction between Cdc13 and telomerase. We propose that Cdc13 participates in two regulatory steps-first positive, then negative-as a result of successive binding of telomerase and the negative regulator Stn1 to overlapping sites on Cdc13. Thus, Cdc13 coordinates synthesis of both strands of the telomere by first recruiting telomerase and subsequently limiting G-strand synthesis by telomerase in response to C-strand replication.