Rare C-to-G mutations occurred at an unexpectedly high frequency during emergence of SARS-CoV-2 delta variant
SARS-CoV-2 possesses a characteristic surface protein, the spike protein, which plays a central role in viral entry into host cells. The evolution of spike protein mutations has been an important factor in the emergence of viral variants with altered transmissibility and immune-evasion properties. Previous studies have shown that SARS-CoV-2 evolution is strongly biased toward certain types of…
The delta variant of SARS-CoV-2 emerged unexpectedly in 2021, causing a major global outbreak. This variant's spike protein, which aids viral entry into host cells, acquired seven amino acid substitutions beyond the common D614G substitution. Two of these substitutions, T19R and P681R, originated from C-to-G nucleotide substitutions, which are typically rare in the evolution of SARS-CoV-2.
Analysis of genomic sequences in public databases showed that C-to-G substitutions are generally rare throughout SARS-CoV-2 evolution. However, the delta variant's spike protein was unusually enriched for this particular type of mutation, with a significant proportion (2 of 7) of substitutions being C-to-G. This unusual enrichment of a typically suppressed mutation type may provide insights into the evolutionary processes behind the emergence of highly transmissible variants.
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