Analyses of gene structures and splicing variants of prmt1 and its vertebrate paralogue prmt8 suggest their molecular evolution

Analyses of gene structures and splicing variants of prmt1 and its vertebrate paralogue prmt8 suggest their molecular evolution

Protein arginine methylation is a posttranslational modification involved in transcriptional regulation, RNA processing and many different cellular processes. There are nine different protein arginine methyltransferases (PRMTs) genes in mammals. PRMT1 is the most conserved and widely distributed PRMT in eukaryotes. PRMT8 is a vertebrate-specific paralogue of PRMT1 and the major difference between the two PRMTs is that PRMT8 contains an extra N-terminus of about 60-90 amino acids in different species. We collected the prmt1 as well as prmt8 genomic and cDNA sequences from typical vertebrate and animal species and constructed the gene structure diagram. A basic 10-exon configuration with exactly the same intron/exon junctions was observed for vertebrate prmt1 and prmt8 as well as some chordate prmt1. Multiple sequence alignments of the amino acid sequences of PRMT1 and PRMT8 clearly illustrated the major differences in N-terminal variable region through evolution. We also collected RNA variants of the two genes. Most of the prmt1 variants in human and mice encode different N-termini due to alternative splicing. However, similar prmt1 variants with missing sequences close to the C-terminus in human (variant 4) and mouse (variant 3) have not been reported in previous publications. A prmt8 variant 2 in primates with an alternative exon 1 was identified in the data base and similar variants can be predicted in primates with conserved protein sequences and genomic localization. We also constructed phylogenetic tree of the prmt1 and prmt8 mRNAs and showed clear vertebrate duplication pattern. Our analyses of the genomic structures and the putative transcriptional variants of prmt1 and prmt8 will help to trace the evolution origin of prmt8 and provide critical information for future experimental designs of these genes.