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

Next, the detailed nucleotide changes of each comparison group were analyzed, and we found that the T-to-C (T:C) transition mutation was enriched in the nucleotide substitutions between WIV04 and RaTG13 (Fig. 1B) . It's reported that the CoVs lacking a 3'-to-5' exoribonuclease (ExoN) accumulated 15 to 20 fold more A:G and U:C transition (14) . What's more, the RNA mutagen 5-fluorouracil (5-FU) treatment will also increase the U:C and A:G transitions. Consequently, this increased T:C mutation implies the ExoN of SARS-CoV-2 may be deactivated compared with that of RaTG13. The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.02.27.969006 doi: bioRxiv preprint Furthermore, we checked whether the ratio of synonymous substitution to missense substitution is increased within SARS-CoV-2 strains. From December 2019 to February 2020, the genome sequences of 108 strains of SARS-CoV-2 virus have been submitted to GISAID database worldwide. Compared with the standard SARS-CoV-2 strain WIV04, total 98 point mutations were detected at 93 nucleotide sites of all SARS-CoV-2 strains with genome sequence available on Feb. 25 2020 (Fig. 1A) . However, only 58 of these nucleotide mutations caused changes in amino acids. Among them, 15 nucleotide substitutions at 14 sites caused changes in 7 amino acids of the spike protein were observed. Consequently, the proportion of synonymous mutations (~40%) among all current reported SARS-CoV-2 strains is similar to that between WIV04 and Bat-SL-CoVZC45 (39.1%), but is dramatically less than that between WIV04 and RaTG13 (90.7%).