HR-HPV E6 alternative RNA splicing. The donor and acceptor splicing sites for the E6 truncated transcripts of different HPV types that possess more than one variant of E6* mRNA. (A) The E6* transcripts identified in HPV16 are E6*I to VI, E6^E7, E6^E7*I and E6^E7*II; (B) Four E6* transcripts have been described for HPV18 termed E6*I to III and E6^E7; (C) E6*I and E6^E4 transcripts are known for HPV31; (D) E6*I to III for HPV33; (E) E6*I and II transcripts for HPV58. All these transcript variants contain a donor splicing site within the E6 open reading frame (ORF), while the acceptor splicing site is contained through the early HPV pre-mRNA (E6, E7, E2 or E4 ORFs). The nucleotide positions of early promoters (p) and early polyadenylation (Poly-A) sequences, as well as the positions of early genes, were obtained from Papillomavirus episteme [8]. The early promoter of HPV58 was obtained from Li Y. et al. 2013 [67]. All the donor and acceptor splicing sites are listed in Table 1.