Relative synonymous codon usage (RSCU) values of CpG-containing codons.

<p>Box plots showing the RSCU values of CpG-containing codons among (a) papillomaviruses and (b) polyomaviruses. CpG-containing codons are shown in red colour. The encoded amino acid is shown in parenthesis. Both group of viruses avoided CpG-containing synonymous codons as 100% (8 out of 8) of these codons had an RSCU value below one. (c) RSCU values of CpG-containing codons among papillomaviruses infecting different host groups: papillomaviruses infecting humans or other mammals had significantly lower RSCU values than those infecting aves/reptiles [0.47(95% CI of 0.42 to 0.52) vs 0.8(95% CI of 0.68 to 0.92); P = 0.0004; 0.55(95% CI of 0.53 to 0.58) vs 0.8(95% CI of 0.68 to 0.92); P = 0.0002]. (d) RSCU values of CpG-containing codons among polyomaviruses infecting different host groups: polyomaviruses infecting humans had significantly lower RSCU values as compared to those infecting other mammals [0.11(95% CI of 0.09 to 0.14) vs 0.17(95% CI of 0.16 to 0.19), P = 0.0007] or aves [0.11(95% CI of 0.09 to 0.14) vs 0.45(95% CI of 0.34 to 0.57); P = 0.0003].