PRMT1-mediated methylation of the Large Drosha Complex regulates microRNA biogenesis

Abstract

MicroRNA (miRNA) biogenesis is a tightly controlled multi-step process operated in the nucleus by the activity of the Large Drosha Complex (LDC). Through high resolution mass spectrometry (MS) analysis we discovered that the LDC is extensively methylated, with 82 distinct methylated sites associated to 16 out of 23 subunits of the LDC. The majority of these modifications occurs on arginine (R)-residues (61), leading to 86 methylation events, while 29 lysine (K)-methylation events occurs on 21 sites of the complex. Interestingly, both depletion and pharmacological inhibition of PRMT1 lead to a widespread alteration of the methylation state of the complex and induce global decrease of miRNA expression, as a consequence of the specific impairment of the pri-to-pre-miRNA processing step. In particular, we show that the reduced methylation of the ILF3 subunit of the complex is linked to its diminished binding to the target pri-miRNAs.Overall, our study uncovers a previously uncharacterized role of R-methylation in the regulation of the LDC activity in mammalian cells, thus affecting global miRNA levels.

PRMTs and miRNAs: functional cooperation in cancer and beyond

“…Moreover, the study revealed that pharmacological blockade of PRMT1 activity resulted in widespread alteration of the arginine methylation state of the complex including proteins such as interleukin enhancer binding factor 3 (ILF3), thus impairing the pri-to-pre-miRNA processing step. This in turn led to a global decrease of miRNA expression [28]. Overall, this study suggests an important role for arginine methylation in modulating the interaction of LDC components with pri-miRNAs, thus uncovering another aspect of the complex, multilayered regulation of miRNA expression by PRMTs at the level of biogenesis.…”

“…Bonaldi et. al demonstrated that 70% of Large Drosha Complex (LDC) proteins were extensively methylated on approximately 82 distinct sites, of which 61 occurred on arginine sites [28]. Moreover, the study revealed that pharmacological blockade of PRMT1 activity resulted in widespread alteration of the arginine methylation state of the complex including proteins such as interleukin enhancer binding factor 3 (ILF3), thus impairing the pri-to-pre-miRNA processing step.…”