The Mechanism Of Pluripotency Maintenance In Stem Cells And The Function Of Long Non-coding RNAs In Tumor Metabolism

Pluripotency of embryonic stem cells (ESCs) is accurately regulated under an intrinsic signaling network, which remains elusive but is required for the potential application of ESCs in research and clinics. Here, we present a retroviral insertion vector pDisrup8, which can cause insertional mutagenesis, to screen and identify novel host genes that are requisite factors for pluripotency of mouse ESCs. We identify that membrane-associated ring finger (C3HC4)5(march5), which is an ubiquitin ligase, is involved in the mESCs identity maintenance. Knockdown of march5leads to decreased expression of pluripotent markers, impaired clonogenicity of mESCs, and low somatic reprogramming efficiency. Meanwhile, we show that march5is transcriptionally activated by klf4and catalyses K63-linked poly-ubiquitination of prkarla, a subunit of protein kinase A, which mediates raf-1phosphorylation at serine259and then inhibits MEK/ERK pathway. The dual inhibition (2i) of MEK/ERK and GSK3is sufficient to sustain propagation of mESCs in the serum-free condition, and we find that ectopic expression of march5or klf4may partially replace MEK inhibitor in the2i system. Altogether, our study uncovers a novel klf4-march5-ERK pathway that plays a role in the sternness maintenance.It is reported that metabolic remodeling occurs during the process of somatic cell reprogramming. L-threonine dehydrogenase (TDH) is one of the most critical enzymes in threonine catabolism which expresses in mouse ES cells uniquely. However, the role of TDH-mediated threonine metabolism in somatic reprogramming still need further investigation. Here we show that TDH indeed functions in this transformation. Knockdown of TDH impairs reprogramming efficiency while overexpression of TDH improves it. Meanwhile, microRNA-9targets TDH and thus impairs iPSCs induction efficiency, and protein arginine methytransferase5(PRMT5) methylates at arginine180of TDH by their direct interaction. PRMT5thus regulates TDH enzyme activity by both methytransferase-dependent and-independent ways, and reprogramming efficiency is improved into a higher level when employing TDH plus PRMT5. These data demonstrate that TDH mediated threonine catabolism involves in somatic cell reprogramming, and this function is regulated post-transcriptionally and post-translationally.Warburg effect is one of the most important phenotype of tumor cells, while its underlying mechanism is still unclear. It is already dicovered that few long non-coding RNAs function in this process, yet it is unknown whether there are more RNAs involved. Here we reported that IDH1-AS1, which is a long non-coding RNA regulated by c-myc, inhibits Warburg effect through stabilizing the dimer of IDH1and then sustaining its enzyme activity. Knock down of IDH1-AS1promotes tumor growth in mouse xenograft models. Altogether, our data shows that IDH1-AS1is a critical factor in Warburg effect and may serve as a valuable therapeutic target.