Regulatory subunit of the mRNA-capping methyltransferase RNMT:RAMAC complex that methylates the N7 position of the added guanosine to the 5'-cap structure of mRNAs (, ). Promotes the recruitment of the methyl donor, S-adenosyl-L-methionine, to RNMT . Regulates RNMT expression by a post-transcriptional stabilizing mechanism . Binds RNA .
Subcellular locations: Nucleus