Sir2 and Fun30 regulate ribosomal DNA replication timing via Mcm helicase positioning and nucleosome occupancy.
Sir2 and Fun30 regulate ribosomal DNA replication timing via Mcm helicase positioning and nucleosome occupancy.
复制标题
Sir2 和 Fun30 通过 Mcm 解旋酶定位和核小体占据来调节核糖体 DNA 复制时间。
DOI：
10.1101/2024.03.21.586113
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发表时间：
2024
期刊：
影响因子：
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通讯作者：
Bedalov,Antonio
中科院分区：
文献类型：
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作者：
Lichauco,Carmina;Foss,EricJ;Gatbonton-Schwager,Tonibelle;Athow,NelsonF;Lofts,BrandonR;Acob,Robin;Taylor,Erin;Lao,Uyen;Miles,Shawna;Bedalov,Antonio
在真核生物异染色质中，晚期复制时间和低转录速率之间的联系是众所周知的，但是这种联系的具体机制仍然不确定。在酿酒酵母中，组蛋白去乙酰基酶Sir2是转录沉默和重复核糖体DNA(RDNA)阵列后期复制所必需的。我们先前已经报道过，在没有Sir2的情况下，去抑制的RNA PolII将MCM复制解旋酶从核糖体起点的装载位置重新定位到邻近核糖体占有率较低的区域。通过发展一种方法来区分紧密间隔的MCM复合体的激活，我们在这里证明了rDNA起始处的移位的MCM比非移位的MCM具有更强的激发倾向。此外，我们发现，重新定位的MCM的激活和相邻核小体的低占有率都严重依赖于FUN30的染色质重塑活性。我们的研究阐明了Sir2延迟复制时间的机制，并首次证明了体内特定复制起点的激活依赖于由单个染色质重构体形成的核小体背景。
The association between late replication timing and low transcription rates in eukaryotic heterochromatin is well known, yet the specific mechanisms underlying this link remain uncertain. In Saccharomyces cerevisiae, the histone deacetylase Sir2 is required for both transcriptional silencing and late replication at the repetitive ribosomal DNA (rDNA) arrays. We have previously reported that in the absence of SIR2, a de-repressed RNA PolII repositions MCM replicative helicases from their loading site at the ribosomal origin, where they abut well-positioned, high-occupancy nucleosomes, to an adjacent region with lower nucleosome occupancy. By developing a method that can distinguish activation of closely spaced MCM complexes, here we show that the displaced MCMs at rDNA origins have increased firing propensity compared to the nondisplaced MCMs. Furthermore, we found that both activation of the repositioned MCMs and low occupancy of the adjacent nucleosomes critically depend on the chromatin remodeling activity of FUN30. Our study elucidates the mechanism by which Sir2 delays replication timing, and it demonstrates, for the first time, that activation of a specific replication origin in vivo relies on the nucleosome context shaped by a single chromatin remodeler.