Studies on Effect of CpG Suppression on Vertebrate Proteome

Abstract

DNA methylation is an epigenetic modification that occurs exclusively at C5 position of the cytosine in eukaryotes in context of CpG dinucleotide. CpG dinucleotides are the hotspots for mutation which causes deamination of cytosine and 5 - methylcytosine. Due to deamination, CpG/CpG is converted into TpG/CpA. This mutation leads to the suppression of CpG and over expression of TpG and CpA. Suppression CpGs in coding reg ions of genome may affect the proteome of eukaryotes having methylated genomes. Codons consisting of CGs can be classified as CGN, NCG and NNC - GNN. The abundance of amino acids encoded by the three types of CG codons have been compared against their expect ed frequency in methylated genomes (Homo sapiens and Mus musculus ) and unmethylated genomes as control( Bacteriophage lambda, Haemophillus Influenza and E.coli. ). The amino acids analysis is not significant. The effects have been showed due to other evolutionary forces. But in di - amino acid analysis, Homo sapiens and mus musculus genome, showing (< 1 O/E ) values lesser than Bacteriophage lambda in total genome and in coding sequence, higher number of di - amino acids showing (<1 O/E ) values in methylate d genomes which indicates the effect of CG suppression in proteomes.