Fig. 2.

Methylation status of homologous CpG sites in the 3′LCR of HPV16, HPV18 and HPV45. The methylation level of each CpG site is represented by a box displaying upper and lower quartiles separated by the median line, and whisker plots. HPV16 displayed a higher level of methylation than HPV18 and HPV45, mainly at E2 binding sites (E2BS#3 and #4). This was statistically different when comparing the homologous CpG sites of HPV16 vs HPV18 (CpG 37 vs 44, p = 0.0018; CpG 43 vs 50, p = 0.0490; and 58 vs 66, p = 0.0109), and HPV18 vs HPV45 (CpG 44 vs CpG41). Analyses were performed with the Mann-Whitney U test.