Ki-67 Contributes to Normal Cell Cycle Progression and Inactive X Heterochromatin in p21 Checkpoint-Proficient Human Cells
Ki-67 Contributes to Normal Cell Cycle Progression and Inactive X Heterochromatin in p21 Checkpoint-Proficient Human Cells
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DOI：
10.1128/mcb.00569-16
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发表时间：
2017-09-01
影响因子：
5.3
通讯作者：
Kaufman, Paul D.
中科院分区：
文献类型：
--
作者：
Sun, Xiaoming;Bizhanova, Aizhan;Kaufman, Paul D.
Ki-67 蛋白被广泛用作肿瘤增殖标志物。然而，Ki-67是否影响细胞周期进程一直存在争议。在这里，我们证明，人 hTERT-RPE1、WI-38、IMR90 和 hTERT-BJ 细胞系和原代成纤维细胞中 Ki-67 的耗竭会减慢进入 S 期的速度，并协调下调与 DNA 复制相关的基因。在 Ki-67 耗尽的 hTERT-RPE1 细胞中，通过同时去除 Rb 检查点蛋白，一些基因表达变化得到部分缓解，但在去除细胞周期抑制剂 p21 后，观察到转录和细胞周期缺陷得到更彻底的抑制。值得注意的是，Ki-67 耗尽后 p21 的诱导是转录和细胞周期分布对 Ki-67 敏感的细胞类型的一致标志。这些反应在不诱导 p21 的细胞中不存在。此外，Ki-67 耗尽后，雌性 hTERT-RPE1 细胞中的一组失活 X (Xi) 染色体表现出异染色质维持受损的几个特征，包括 H3K27me3 和 H4K20me1 标记减少。这些染色质改变仅限于远离核纤层的 Xi 染色体，在检查点缺陷的 293T 细胞中未观察到。总而言之，我们的结果表明，Ki-67 在 p21 检查点熟练的人类细胞中整合了正常的 S 期进展和 Xi 异染色质维持。
The Ki-67 protein is widely used as a tumor proliferation marker. However, whether Ki-67 affects cell cycle progression has been controversial. Here we demonstrate that depletion of Ki-67 in human hTERT-RPE1, WI-38, IMR90, and hTERT-BJ cell lines and primary fibroblast cells slowed entry into S phase and coordinately downregulated genes related to DNA replication. Some gene expression changes were partially relieved in Ki-67-depleted hTERT-RPE1 cells by codepletion of the Rb checkpoint protein, but more thorough suppression of the transcriptional and cell cycle defects was observed upon depletion of the cell cycle inhibitor p21. Notably, induction of p21 upon depletion of Ki-67 was a consistent hallmark of cell types in which transcription and cell cycle distribution were sensitive to Ki-67; these responses were absent in cells that did not induce p21. Furthermore, upon Ki-67 depletion, a subset of inactive X (Xi) chromosomes in female hTERT-RPE1 cells displayed several features of compromised heterochromatin maintenance, including decreased H3K27me3 and H4K20me1 labeling. These chromatin alterations were limited to Xi chromosomes localized away from the nuclear lamina and were not observed in checkpoint-deficient 293T cells. Altogether, our results indicate that Ki-67 integrates normal S-phase progression and Xi heterochromatin maintenance in p21 checkpoint-proficient human cells.