miR-294/miR-302 Promotes Proliferation, Suppresses G1-S Restriction Point, and Inhibits ESC Differentiation through Separable Mechanisms

Abstract

The miR-294/miR-302 microRNAs promote the abbreviated G1 phase of the embryonic stem cell (ESC) cell cycle and suppress differentiation induced by let-7. Here we evaluated the role of the Retinoblastoma (Rb) family proteins in these settings. Under normal growth conditions miR-294 promoted the rapid G1-S transition independent of the Rb family. In contrast, miR-294 suppressed the further accumulation of cells in G1 in response to nutrient deprivation and cell-cell contact in an Rb dependent fashion. We uncovered five additional miRNAs (miRs-26a, -99b, -193, -199a-5p, and 218) that silenced ESC self-renewal in the absence of other miRNAs, all of which were antagonized by miR-294/302. Four of the six differentiation-inducing miRNAs induced an Rb-dependent G1 accumulation. However, all six still silenced self-renewal in the absence of the Rb proteins. These results show that the miR-294/miR-302 family acts through Rb dependent and independent pathways to regulate the G1 restriction point and the silencing of self-renewal respectively.

ADAR1 is required for differentiation and neural induction by regulating microRNA processing in a catalytically independent manner

“…The first group of miRNAs was reported to be highly expressed in undifferentiated hESCs but significantly downregulated upon differentiation, such as miR302s [43][44][45]. In our studies, these miRNAs were upregulated in undifferentiated H9 cells after ADAR1 knockdown.…”

“…We first excluded the role of transcriptional regulation of ADAR1 on miRNA processing. On one hand, loss of ADAR1 had no effect on the expression of oct4, sox2, nanog and rex1 (Supplementary information, Figure S1D and Table S1), which are known as upstream regulators of the pri-miR302 promoter [45], excluding the possibility that the upregulation of miR302s is caused by upregulation of ESC-specific transcriptional factors in ADAR1 KD H9 cells. On the other hand, we found that knockdown of ADAR1 had no significant effect on the promoter activity of pri-miR302 (Supplementary information, Figure S5C), suggesting that ADAR1 is unlikely to be involved in the transcriptional regulation of pri-miR302.…”

“…In addition, the repression on miR302s by ADAR1 was specific, as the expression of other miRNAs was not altered after ADAR1 depletion (Supplementary information, Figure S5B). It is well known that self-renewal-related miR-302s promote ESC proliferation and suppress differentiation [45,46]; thus the delayed downregulation of miR-302s upon ADAR1 depletion could lead to the suppression of hESC differentiation. Furthermore, some miRNAs, such as miR-96 and miR-200s, that repress neural induction [36], were also upregulated in ADAR1 KD samples (Supplementary information, Table S5).…”

A Helm model for microRNA regulation in cell fate decision and conversion

“…Thus, these ESC-specific miRNAs can strongly promote or directly induce the reprogramming of somatic cells to pluripotency [70][71][72][82][83][84]. Mechanistically, these miRNAs have been shown to regulate various cellular processes, including cell cycle, differentiation, mesenchymal-to-epithelial transition (MET), epigenetic regulation, cell signaling and vesicular transport [82,[85][86][87][88][89][90][91], all of which are critical for the establishment and maintenance of pluripotency.…”

Traditional Chinese Medicine Baicalin Suppresses mESCs Proliferation through Inhibition of miR-294 Expression

“…The proliferation ability of ESCs is closely related to the regulation of ESC cell cycle, and ESCs are characterized with a short G1 period [3]. Some of the somatic cells like bone marrow, liver, and skin cells, have a greater regeneration and proliferation potential with short G1 period, while most of the other somatic cells regeneration potential is considered to be low with a long quiescent G0 phase and the proliferation ability is regarded as poor [3]. Cell cycle regulation has two main restriction point, G1/S restriction point and G2/M restriction point.…”