Biochemical analysis of the arginine methylation of high molecular weight fibroblast growth factor-2

The post-translational methylation of the N-terminally extended or high mol ecular weight (HMW) forms of fibroblast growth factor-2 (FGF-2) has been sh own to affect the nuclear accumulation of the growth factor. In this study, we determined the extent and position of methyl groups in HMW FGF-2. Using mass spectrometry and amino acid sequence analysis, we have shown that the 22- and 22.5-kDa forms of HMW FGF-2 contain five dimethylated arginines lo cated at positions -22, -24, -26, -36, and -38 using the methionine residue normally used to initiate the 18-kDa form as position 0. The 24-kDa form o f HMW FGF-2 contains seven to eight dimethylated arginines located at posit ions -48, -50, and -52, in addition to positions -22, -24, -26, -36, and -3 8, In vitro methylation reactions demonstrate that the N-terminal extension of HMW FGF-8 acts as a specific substrate for yeast Hmt1p and human HRMT1L 2 arginine methyltransferases. These findings indicate that HMW FGF-8, with the presence of five or more dimethylated Gly-Arg-Gly repeats, contains an RGG box-like domain, which may be important for protein-protein and/or pro tein-RNA interactions.