Human papillomavirus type 33 in a tonsillar carcinoma generates its putative E7 mRNA via two E6* transcript species which are terminated at different early region poly(A) sites

Abstract

Human papillomavirus type 33 (HPV-33)-specific early region transcripts in a tonsillar carcinoma were analyzed by using the RNA polymerase chain reaction method. A total of five cDNA species including species with potential to encode E6*I, E6*II, and E6*III, could be identified. As determined by 3' cDNA end mapping, one E6*I cDNA species was found to utilize a novel early region poly(A) site and was polyadenylated at or near the putative initiation codon of the El open reading frame (ORF). Compared with the HPV-16 and HPV-18 E6* mRNAs, the HPV-33 E6*I and E6*II species utilize different splice acceptor sites, the latter being localized writhin the E7 ORF. Furthermore, HPV-33 E6* mRNAs were found to contain a short overlapping ORF resulting in alternative coding potentials if translation were to start at an internal AUG codon within the E6 region. These results indicate that like HPV-16 and HPV-18, HPV-33 generates E6* mRNAs which may serve as efficient mRNAs for E7. However, HPV-33 has the ability to generate its putative E7 mRNAs by the utilization of two early region poly(A) sites, which offers the possibility of expressing E7 in different ways.

The Transcription Map of Human Papillomavirus Type 18 during Genome Replication in U2OS Cells

“…Papillomaviruses encode a number of transcription regulators that control the levels of different viral transcripts and thus help to regulate viral genome copy number during amplification. The most studied and primal regulator is the E8 ∧ E2 protein, which has been previously described in BPV1, in several Alpha HPVs (18, 31, 11, 16), in Mu-papillomavirus HPV 1 and in Beta-papillomavirus HPV5 [23] , [32] [33] , [34] , [35] , [36] , [37] , [38] . E8 ∧ E2 consists of a short E8 product (11 amino acids) that is fused to the C-terminal part of the E2 protein, which contains DNA binding and dimerization domains.…”

Translation of the human papillomavirus type 16 E7 oncoprotein from bicistronic mRNA is independent of splicing events within the E6 open reading frame

“…Thus, although HPV-16 E7 can be produced from either full-length bicistronic or spliced transcripts, the structures of the transcripts appear to disallow high-level synthesis of E7 protein. The structures of spliced HPV-18 and HPV-33 also seem to conspire to limit E7 expression: in HPV-18 the E6* spliced product contains a minicistron in the space between the E6* and E7 ORFs (42), and in HPV-33 the E6*I ORF actually terminates closer to the E7 AUG than does the full-length E6 ORF (51). These structures suggest that, as with HPV-16, HPV-18 and -33 splicing does not function to increase the template efficiency for E7 translation.…”

Detection of high‐risk human papillomavirus E6 and E7 oncogene transcripts in cervical scrapes by nested RT‐polymerase chain reaction

“…The HPV 59 RT-PCR reverse primer was later redesigned at a position 10 nucleotides downstream of the original primer. At the time the assay was established, the only splice sites that were known were from HPV types 16, 18, 31, 33 and 51 [Cole and Streeck, 1986;Smotkin and Wettstein, 1986;Smotkin et al, 1989;Lungu et al, 1991;Snijders et al, 1992;Czegledy et al, 1994]. The splice sites of all the other high-risk HPV genotypes were deduced from these published sequences and primers were selected accordingly.…”

“…Uniformity of this splicing pattern has been demonstrated in cervical squamous cell carcinomas, the derived cell lines and CIN lesions [Cornelissen et al, 1990]. In other high-risk HPV genotypes (types 18, 31, 33, 35, 51, 52, 56, 58 and 59), only one splice product has been described [Snijders et al, 1992;Czegledy et al, 1994;Nakagawa et al, 2000]. The splicing pattern and splice sites in high-risk genotypes 39, 45, 66 and 68 have not yet been described.…”