E-Ras improves the efficiency of reprogramming by facilitating cell cycle progression through JNK–Sp1 pathway

Abstract

We have previously shown that pluripotent stem cells can be induced from adult somatic cells which were exposed to protein extracts isolated from mouse embryonic stem cells (mESC). Interestingly, generation of induced pluripotent stem (iPS) cells depended on the background of ES cell lines; possible by extracts from C57, but not from E14. Proteomic analysis of two different mES cell lines (C57 and E14) shows that embryonic Ras (E-Ras) is expressed differently in two mES cell lines; high level of E-Ras only in C57 mESC whose extracts allows iPS cells production from somatic cells. Here, we show that E-Ras augments the efficiency in reprogramming of fibroblast by promoting cell proliferation. We found that over-expression of E-Ras in fibroblast increased cell proliferation which was caused by specific up-regulation of cyclins D and E, not A or B, leading to the accelerated G1 to S phase transition. To figure out the common transcription factor of cyclins D and E, we used TRANSFAC database and selected SP1 as a candidate which was confirmed as enhancer of cyclins D and E by luciferase promoter assay using mutants. As downstream signaling pathways, E-Ras activated only c-Jun N-terminal kinases (JNK) but not ERK or p38. Inhibition of JNK prevented E-Ras-mediated induction of pSP1, cyclins D, E, and cell proliferation. Finally, E-Ras transduction to fibroblast enhanced the efficiency of iPS cell generation by 4 factors (Oct4/Klf4/Sox2/C-myc), which was prevented by JNK inhibitor. In conclusion, E-Ras stimulates JNK, enhances binding of Sp1 on the promoter of cyclins D and E, leading to cell proliferation. E-Ras/JNK axis is a critical mechanism to generate iPS cells by transduction of 4 factors or by treatment of mESC protein extracts.

Hint1 expression inhibits proliferation and promotes radiosensitivity of human SGC7901 gastric cancer cells

“…This cascade participates in the regulation of a number of processes, including cell adhesion, cell cycle progression, cell migration, cell survival, differentiation, metabolism, proliferation and transcription ( 11 , 12 ). ERKs directly phosphorylate multiple transcription factors, including the ETS transcription factor family, c-Jun and c-Myc ( 15 – 17 ). ERK also phosphorylates and activates the 90 kDa ribosomal S6 kinase (p90Rsk), which, in turn, leads to the activation of the transcription factor cAMP response element binding protein ( 18 ).…”

Decreased expression level and DNA‑binding activity of specificity protein 1 via cyclooxygenase‑2 inhibition antagonizes radiation resistance, cell migration and invasion in radiation‑resistant lung cancer cells

“…4A ). As c-Jun N-terminal kinase (JNK) has been demonstrated to increase Sp1 protein stability, the inhibition of JNK may decrease E-Ras-induced Sp1 phosphorylation, and therefore decrease the protein stability of Sp1 ( 34 ). The present study hypothesized that the JNK signaling pathway mediated the celecoxib-induced downregulation of Sp1.…”

Understanding the Role of the Transcription Factor Sp1 in Ovarian Cancer: from Theory to Practice

“…E-Ras was found to enhance binding of Sp1 on the cyclins to promote cell proliferation and reprogramming. This is identified as a way to increase the efficiency of IPSC derivation protocols [107]. Regeneration existing in the epicenter of reprogramming, has been studied for decades.…”