Specific sequences within arginine-glycine-rich domains affect mRNA-binding protein function.

The discovery of roles for arginine methylation in intracellular transport and mRNA splicing has focused attention on the methylated arginine-glycine (RG)-rich domains found in many eukaryotic RNA-binding proteins. Sequence similarity among these highly repetitive RG domains, combined with interactions between RG-rich proteins, raises the question of whether these regions are general interaction motifs or whether there is specificity within these domains. Using the essential Saccharomyces cerevisiae mRNA-binding protein Npl3 (ScNpl3) as a model system, we first tested the importance of the RG domain for protein function.

Arginine methylation of yeast mRNA-binding protein Npl3 directly affects its function, nuclear export, and intranuclear protein interactions.

Arginine methylation can affect both nucleocytoplasmic transport and protein-protein interactions of RNA-binding proteins. These effects are seen in cells that lack the yeast hnRNP methyltransferase (HMT1), raising the question of whether effects on specific proteins are direct or indirect. The presence of multiple arginines in individual methylated proteins also raises the question of whether overall methylation or methylation of a subset of arginines affects protein function.