Department of Molecular Genetics and Microbiology University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.
Nucleic Acids Res. 2021 Jan 25;49(2):864-878. doi: 10.1093/nar/gkaa1148.
Quiescent cells reside in G0 phase, which is characterized by the absence of cell growth and proliferation. These cells remain viable and re-enter the cell cycle when prompted by appropriate signals. Using a budding yeast model of cellular quiescence, we investigated the program that initiated DNA replication when these G0 cells resumed growth. Quiescent cells contained very low levels of replication initiation factors, and their entry into S phase was delayed until these factors were re-synthesized. A longer S phase in these cells correlated with the activation of fewer origins of replication compared to G1 cells. The chromatin structure around inactive origins in G0 cells showed increased H3 occupancy and decreased nucleosome positioning compared to the same origins in G1 cells, inhibiting the origin binding of the Mcm4 subunit of the MCM licensing factor. Thus, quiescent yeast cells are under-licensed during their re-entry into S phase.
静止细胞停留在 G0 期，其特征是缺乏细胞生长和增殖。这些细胞保持存活，并在接收到适当的信号时重新进入细胞周期。我们使用细胞静止的芽殖酵母模型，研究了 G0 期细胞恢复生长时启动 DNA 复制的程序。静止细胞中复制起始因子的水平非常低，并且它们进入 S 期直到这些因子重新合成。与 G1 细胞相比，这些细胞的 S 期更长，与复制起点的激活数量减少相关。与 G1 细胞中的相同起点相比，G0 细胞中无活性起点周围的染色质结构显示出更高的 H3 占有率和更低的核小体定位，抑制了 Mcm4 亚基的 MCM 许可因子的起点结合。因此，静止的酵母细胞在重新进入 S 期时处于未许可状态。
