Department of Biochemistry and Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA, USA.
Cell Cycle. 2009 Nov 15;8(22):3729-41. doi: 10.4161/cc.8.22.10033. Epub 2009 Nov 10.
microRNAs (miRNAs) regulate numerous physiological processes such as cell division and differentiation in many tissue types including stem cells. To probe the role that miRNAs play in regulating processes relevant to embryonic stem cell biology, we used RNA interference to silence DICER and DROSHA, the two main miRNA processing enzymes. Consistent with a role for miRNAs in maintaining normal stem cell division and renewal, we found that perturbation of miRNA pathway function in human embryonic stem cells (hESCs) attenuates cell proliferation. Normal cell growth can be partially restored by introduction of the mature miRNAs miR-195 and miR-372. These miRNAs regulate two tumor suppressor genes, respectively: WEE1, which encodes a negative G2/M kinase modulator of the CycB/CDK complex and CDKN1A, which encodes p21, a CycE/CDK cyclin dependent kinase inhibitor that regulates the G1/S transition. We show that in wild-type hESCs, WEE 1 levels control the rate of hESC division, whereas p21 levels must be maintained at a low level for hESC division to proceed. These data support a model for hESC cell cycle control in which miRNAs regulate negative cell cycle modulators at two phases of the cell cycle to ensure proper replenishment of the stem cell population.
微小 RNA（miRNAs）在包括干细胞在内的许多组织类型中调节着细胞分裂和分化等多种生理过程。为了探究 miRNAs 在调节与胚胎干细胞生物学相关的过程中所起的作用，我们使用 RNA 干扰使 miRNA 加工酶 DICER 和 DROSHA 沉默。miRNAs 在维持正常干细胞分裂和更新中的作用一致，我们发现 miRNA 通路功能在人胚胎干细胞（hESCs）中的扰动会减弱细胞增殖。通过引入成熟的 miRNAs miR-195 和 miR-372 可以部分恢复正常的细胞生长。这些 miRNA 分别调节两个肿瘤抑制基因：编码 CycB/CDK 复合物负性 G2/M 激酶调节剂的 WEE1 和编码细胞周期蛋白依赖性激酶抑制剂 p21 的 CDKN1A，后者调节 G1/S 期过渡。我们表明，在野生型 hESCs 中，WEE1 水平控制 hESC 分裂的速度，而 p21 水平必须维持在低水平才能进行 hESC 分裂。这些数据支持了 hESC 细胞周期控制的模型，其中 miRNAs 在细胞周期的两个阶段调节负性细胞周期调节剂，以确保干细胞群体的适当补充。
