Cross-talk between PRMT1-mediated methylation and ubiquitylation on RBM15 controls RNA splicing

Abstract

RBM15, an RNA binding protein, determines cell-fate specification of many tissues including blood. We demonstrate that RBM15 is methylated by protein arginine methyltransferase 1 (PRMT1) at residue R578, leading to its degradation via ubiquitylation by an E3 ligase (CNOT4). Overexpression of PRMT1 in acute megakaryocytic leukemia cell lines blocks megakaryocyte terminal differentiation by downregulation of RBM15 protein level. Restoring RBM15 protein level rescues megakaryocyte terminal differentiation blocked by PRMT1 overexpression. At the molecular level, RBM15 binds to pre-messenger RNA intronic regions of genes important for megakaryopoiesis such as GATA1, RUNX1, TAL1 and c-MPL. Furthermore, preferential binding of RBM15 to specific intronic regions recruits the splicing factor SF3B1 to the same sites for alternative splicing. Therefore, PRMT1 regulates alternative RNA splicing via reducing RBM15 protein concentration. Targeting PRMT1 may be a curative therapy to restore megakaryocyte differentiation for acute megakaryocytic leukemia.DOI: http://dx.doi.org/10.7554/eLife.07938.001

PRMT1-RBM15 axis regulates megakaryocytic differentiation of human umbilical cord blood CD34+ cells

“…The present study demonstrated that DB75 rescues PRMT1-blocked MK differentiation via promoting RBM15 expression. Our previous data indicated that PRMT1 methylates RBM15 at R578 and promotes RBM15 protein level degradation via ubiquitylation in a leukemia cell line (8). The present study also suggested that PRMT1 reduces RBM15 expression in human stem cells, which may contribute to defective megakaryopoiesis.…”

“…Therefore, PRMT1-mediated MK blockage may contribute to leukemogenesis. PRMT1 promotes the production of MK-erythroid progenitor cells; however, PRMT1 has to be turned off to generate mature, polyploidy CD41 + CD42 + MK cells (8). The present study demonstrated that PRMT1 negatively modulated differentiation toward the megakaryocytic lineage in human CD34 + hematopoietic cells.…”

“…RNA binding motif protein 15 (RBM15) is required for the long-term maintenance of the homeostasis of hematopoietic stem cells and for MK differentiation (6,7). RBM15 stability is controlled by PRMT1 via CNOT4-mediated ubiquitylation (8). To investigate the biological significance of PRMT1-mediated methylation of RBM15, the present study analyzed the role of the PRMT1-RBM15 axis in megakaryopoiesis.…”

Protein arginine methyltransferase 1 (PRMT1) represses MHC II transcription in macrophages by methylating CIITA

“…At this point, it is not clear what arginine residues within CIITA are targeted by PRMT1. In addition, it remains undetermined whether PRMT1-induced CIITA degradation is solely a result of PRMT1-dependent arginine methylation or a secondary effect contingent on communications with other types of post-translational modifications since PRMT1-dependent arginine methylation has been shown to form crosstalk with acetylation2627, ubiquitination2829, and phosphorylation3031. It has been previously shown that CIITA poly-ubiquitination plays a role in regulating its stability20, although CIITA mono-ubiquitination could enhance its activity without altering its half-life32.…”

Small Molecule Inhibitors of Protein Arginine Methyltransferases

“…Compound 16 , a close structural analogue of DB75, was used as a tool compound to inhibit PRMT1-mediated Smad6 methylation, revealing that the methyltransferase activity of PRMT1 is essential for bone morphogenetic proteins (BMP)-induced Smad1/Smad5 phosphorylation and downstream signaling activation [123]. Recently, we found that DB75 inhibits PRMT1-mediated putative RNA-binding protein 15 (RBM15) methylation at residue R578 [124]. Arginine methylation of RBM15 leads to its ubiquitination by the E3 ligase CNOT4 and subsequent degradation.…”