Biochemical Investigation of the Interaction of pICln, RioK1 and COPR5 with the PRMT5–MEP50 Complex

Abstract

The PRMT5–MEP50 methyltransferase complex plays a key role in various cancers and is regulated by different protein–protein interactions. Several proteins have been reported to act as adaptor proteins that recruit substrate proteins to the active site of PRMT5 for the methylation of arginine residues. To define the interaction between these adaptor proteins and PRMT5, we employed peptide truncation and mutation studies and prepared truncated protein constructs. We report the characterisation of the interface between the TIM barrel of PRMT5 and the adaptor proteins pICln, RioK1 and COPR5, and identify the consensus amino acid sequence GQF[D/E]DA[E/D] involved in binding. Protein crystallography revealed that the RioK1 derived peptide interacts with a novel PPI site.

Molecular basis for substrate recruitment to the PRMT5 methylosome

“…The second b-turn (''2'' in Figure 2D) forces the Gln and Phe residues into the ''stacked'' conformation required for interaction with the shallow pocket described above. Following preprint of these data, an independent PBM peptide-bound crystal structure was reported with the same binding mechanism described here, demonstrating the reproducibility of our data (Krzyzanowski et al, 2021).…”

MYBL1 induces transcriptional activation of ANGPT2 to promote tumor angiogenesis and confer sorafenib resistance in human hepatocellular carcinoma

“…The protein arginine methyltransferase 5(PRMT5) is responsible for regulation of multiple biological processes including transcription, RNA splicing, metabolic signaling, differentiation, and spliceosome assembly [8,9]. PRMT5 always complexed with the WD-repeat protein MEP50 and binding to the catalytic site to produce methylarginine of histone or target protein [10,11]. H3R2me1 or H3R2me2s modified by PRMT5-mediated transcriptional activation is always recruited the WDR5 methyltransferase complexes, subsequently induced histone H3K4me3 which is recognized by the RNA polymerase II transcription complex on the promoters of target genes [12].…”

Discovery and Biological Characterization of PRMT5:MEP50 Protein–Protein Interaction Inhibitors

“…These data suggest that targeting PRMT5 and its interacting proteins including substrate adaptors such as pICln, COPR5, and RIOK1 may offer a unique and potentially specific approach to target PRMT5 in a context-specific manner by exploiting this unique cofactor dependency. Indeed, at the time of article preparation, three recent reports established a PRMT5 substrate adapter-binding motif and subsequent development of an inhibitor targeting the said motif to disrupt PRMT5:RIOK1 interactions, − although the clinical implication of these inhibitors remains unclear. Because PRMT5 represents a valuable therapeutic target with several phase I clinical trials currently underway in solid and blood cancers and because PRMT5 is the only PRMT of nine family members that requires a cofactor (MEP50) and/or other factors for function, targeting the PRMT5:MEP50 protein–protein interaction (PPI) may offer a specific approach as opposed to the catalytic or pan-MT inhibitors. − …”