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In order to determine the physiological roles of WT (wild type) EWSR1, Dr. Lee\'s group established a conventional Ewsr1 KO mouse . Since then, the Ewsr1 KO (−/−) mouse model has successfully been utilized to decipher many important in vivo roles of EWSR1 (Fig. 1).
EWSR1 deficiency alters microRNA processing via Drosha As a part of epigenetic components, microRNAs (miRNAs) play significant roles on regulating gene expression. miRNAs are transcribed by RNA polymerase II from the genome. miRNA is a short non-coding RNA consisting of about 22 nucleotides and plays a role as a post-transcriptional regulator in gene expression. miRNAs bind to complementary target sequence of messenger RNA (mRNA), and degrade target mRNAs or inhibit their translation into proteins. Long primary transcript miRNAs (called pri-miRNAs) are processed in the nucleus by DROSHA, a member of the ribonuclease III family (RNase III), and converted into precursor miRNAs (pre-miRNAs) . In turn, the pre-miRNA is being exported to the cytoplasm via XPO5/EXPORTIN‑5 and is further processed by DICER1, a double-stranded RNA-specific endoribonuclease . Although many studies have characterized the role of miRNAs under normal and disease conditions, no studies have shown whether EWSR1 is involved in the regulation of miRNA levels. Our group found for the first time that EWSR1 indirectly regulates the expression of microRNAs (miRNAs) via an induction of DROSHA (Fig. 3) . Ewsr1 deficiency elevates expression of Drosha and, in turn, increases miR‑29b and miR‑18b levels. Interestingly, both miR‑29b and miR‑18b directly target collagen IV alpha 1 (Col4a1) and Oseltamivir phosphate growth factor (CTGF) mRNAs and reduce their mRNA levels by negatively regulating the post-transcriptional pathway in Ewsr1 KO mouse MEFs. Consequently, the increased expression of Drosha, miR‑29b, and miR‑18b and the reduction of Col4a1 and CTGF lead to impaired epidermal and dermal development, resulting in the abnormal skin development and aging in the Ewsr1 KO mice. In contrast, loss of Drosha function restores Col4a1 and CTGF protein levels by normalizing miR‑29b, and miR‑18b expression in Ewsr1 KO mouse MEFs. Collectively, our previous study indicates that EWSR1 presents the epigenetic effector function in the post-transcriptional regulation of Col4a1 and CTGF via the Drosha-miRNA-dependent pathway. This evidence proves a novel epigenetic role of EWSR1 in miRNA biogenesis and dermal morphogenesis.
EWSR1 regulates autophagy via an epigenetic modulation of UVRAG Autophagy is a well-known intracellular self-digestive process that disassembles dysfunctional macro-molecular components to maintain cellular homeostasis [49,50]. In response to stress, autophagy often plays a key role by removing damaged organelles and recycling nutrients and energy within the cell [, , ]. Moreover, it has been reported that excessive activation or inactivation of autophagy is associated with various diseases, including neurodegenerative disorders and cancer [51,52,54,55]. miRNAs are known to regulate the autophagy-related genes and their activities. Also, miRNAs modulate autophagy at different stages such as autophagic induction, vesicle nucleation, vesicle elongation and completion, by targeting autophagy complexes via different miRNAs [, , ]. Recently, although there has been plenty of evidence that miRNAs modulate autophagy, their target genes and precise roles in the autophagy pathways have not been fully defined yet. In this context, our group previously investigated whether EWSR1 plays a role in the autophagy pathway or not using Ewsr1 null (−/−) MEFs. Two novel findings were identified as follows: First, Ewsr1 deficiency up regulates microprocessor complexes and miR125a and miR351. Interestingly, EWSR1 indirectly regulates UVRAG expression at the post-transcriptional level via miR125a and miR351 . Second, UVRAG dysfunction subsequently leads to an aberrant deregulation of autophagy pathway. Decreased expression levels of Uvrag mRNA and protein are correlated with the altered autophagy pathway in Ewsr1 KO (−/−) mice.