RaTG13, MP789, and RmYN02 are the strains closest to SARS-CoV-2, and their existence came to light only after the start of the pandemic. Their genomes have been used to support a natural origin of SARS-CoV-2 but after a close examination all of them exhibit several issues. We specifically address the presence in RmYN02 and closely related RacCSxxx strains of a claimed natural PAA/PVA amino acid insertion at the S1/S2 junction of their spike protein at the same position where the PRRA insertion in SARS-CoV-2 has created a polybasic furin cleavage site. We show that RmYN02/RacCSxxx instead of the claimed insertion carry a 6-nucleotide deletion in the region and that the 12-nucleotide insertion in SARS-CoV-2 remains unique among Sarbecoviruses. Also, our analysis of RaTG13 and RmYN02's metagenomic datasets found unexpected reads which could indicate possible contamination. Because of their importance to inferring SARS-CoV-2's origin, we call for a careful reevaluation of RaTG13, MP789 and RmYN02 sequencing records and assembly methods.
Keywords: Pangolin CoV MP789; RaTG13; RmYN02; SARS-CoV-2; furin cleavage site; origin; peer review.
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