| Screening PRMT 1 substrates from a lambdagt 11 HeLa cDNA library , we found that more than half of the 48 cDNA clones obtained encode putative RNA binding proteins that have RGG ( arginine glycine glycine ) motifs , such as hnRNP R ( heterogeneous nuclear ribonucleoprotein R ) and hnRNP K . ^^^ |