Comparative genomic analysis revealed specific mutation pattern between human coronavirus SARS-CoV-2 and Bat-SARSr-CoV RaTG13

Longxian Lv; Gaolei Li; Jinhui Chen; Xinle Liang; Yudong Li

The specific mutation pattern may caused by the loss function of RNA 3'-to-5' exoribonuclease (ExoN). Moreover, as the SARS-CoV-2 was supposed to be originated from Bat-SARSr-CoV RaTG13, the increased synonymous substitution between SARS-CoV-2 and RaTG13 strain suggested the SARS-CoV-2 genome was under stronger negative (purifying) selection. We also detected some sites in spike protein was experiencing positive selection. These observations suggest that adaptive evolution might contribute to its host shifts. However, as the RNA mutagen (e.g. 5-FU) could induce the same mutation pattern, the mechanism of the mutation pattern observed between SARS-CoV-2 and RaTG13 should be further investigated in future work. The number of amino acid changes. RSCUdist: the RSCU distance of spike protein; ENc: effective number of codons; S ident(%): the percent identity of S protein sequence between different coronaviruses. The NT/AA ratio between WIV04/RaTG13 was statistically significant higher (Chi-squared test, P<0.01) than that of other strain pairs.