痘苗病毒 TopIB 蛋白在酵母中引发的缺失。

Deletions initiated by the vaccinia virus TopIB protein in yeast.

机构信息

Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.

Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.

出版信息

DNA Repair (Amst). 2024 May;137:103664. doi: 10.1016/j.dnarep.2024.103664. Epub 2024 Mar 6.

Abstract

The type IB topoisomerase of budding yeast (yTop1) generates small deletions in tandem repeats through a sequential cleavage mechanism and larger deletions with random endpoints through the nonhomologous end-joining (NHEJ) pathway. Vaccinia virus Top1 (vTop1) is a minimized version of the eukaryal TopIB enzymes and uniquely has a strong consensus cleavage sequence: the pentanucleotide (T/C)CCTTp↓. To define the relationship between the position of TopIB cleavage and mutagenic outcomes, we expressed vTop1 in yeast top1Δ strains containing reporter constructs with a single CCCTT site, tandem CCCTT sites, or CCCTT sites separated by 42 bp. vTop1 cleavage at a single CCCTT site was associated with small, NHEJ-dependent deletions. As observed with yTop1, vTop1 generated 5-bp deletions at tandem CCCTT sites. In contrast to yTop1-initiated deletions, however, 5-bp deletions associated with vTop1 expression were not affected by the level of ribonucleotides in genomic DNA. vTop1 expression was associated with a 47-bp deletion when CCCTT sites were separated by 42 bp. Unlike yTop1-initiated large deletions, the vTop1-mediated 47-bp deletion did not require NHEJ, consistent with a model in which re-ligation of enzyme-associated double-strand breaks is catalyzed by vTop1.

摘要

芽殖酵母的拓扑异构酶 IB 型(yTop1)通过顺序切割机制产生串联重复序列的小缺失,通过非同源末端连接(NHEJ)途径产生随机末端的较大缺失。痘病毒拓扑异构酶 1(vTop1)是真核 TopIB 酶的简化版本,具有独特的强一致切割序列:五核苷酸(T/C)CCCTTp↓。为了定义 TopIB 切割位置与诱变结果之间的关系,我们在含有单个 CCCTT 位点、串联 CCCTT 位点或由 42bp 分隔的 CCCTT 位点的报告构建体中表达 vTop1 在酵母 top1Δ 菌株中。vTop1 在单个 CCCTT 位点的切割与小的、依赖于 NHEJ 的缺失有关。与 yTop1 观察到的情况一样,vTop1 在串联 CCCTT 位点产生 5bp 的缺失。然而,与 vTop1 表达相关的 5bp 缺失与 yTop1 引发的缺失不同,不受基因组 DNA 中核苷酸水平的影响。当 CCCTT 位点相隔 42bp 时,vTop1 表达与 47bp 的缺失有关。与 yTop1 引发的大缺失不同,vTop1 介导的 47bp 缺失不需要 NHEJ,这与酶相关双链断裂的再连接由 vTop1 催化的模型一致。

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