Analysis on M genes variation rules of SARS-CoV

Objective To discover the variations rules of M genes through sequencing the M gene of SARS-CoV GD322 isolate and to compare it with those of published on GenBank.Methods RNA was extracted from SARS-CoV GD322 strain and used for RT-PCR,then the PCR prducts were cloned into pGEM-T vector and transformed DH5α,with which was followed M gene sequencing.This M gene sequence and other 81 M genes published on GenBank were used to compare with the M gene of TOR2 with Clustal X,from which the variation rules of M genes were gotten.Then,predicted the α turn and the possible B cell epitopes with Protean program and analyzed the variations effect on them.Results After sequencing the gene of GD322 isolate(AY702026) and analyzing those published 81 M genes,TOR2 was selected as the reference strain.Among the 82 M genes,36 isolates' M genes were same as that of TOR2,5 isolates synonymous mutation and 40 isolates nonsynonymous mutation.11 nucleotide mutation sites were discovered in the 82 M genes,9 of which were nonsynonymous mutation and 2 synonymous mutation.The results of predicting the α turn and the B cell epitopes of M genes of Frankfurt 1 and TW5 showed no differences to those of TOR2. Conclusion Though the variations of SARS-CoV M genes are of gradually increasing trend during the course of epidemic spread,the total mutation rate is quite small and the M gene sequences are considerably stable,the isolates related to M hotel varied less than those with no relation to.The variations of M genes have hardly affected the antigenicity of M protein.