A promoter within the E6 ORF of human papillomavirus type 16 contributes to the expression of the E7 oncoprotein from a monocistronic mRNA.
Human papillomavirus type 16 (HPV-16) has the capacity to transform human primary keratinocytes. Maintenance of the transformed phenotype requires constitutive expression of the oncoproteins E6 and E7. The low-risk HPV types express E7 from monocistronic mRNA, but for the high-risk types, no mRNA that encodes E7 as the first open reading frame (ORF) has been identified. We recently identified a transcription initiation site within the E6 ORF of HPV-16 at nt 542. In the present study we have characterized the P542 promoter, which putatively controls monocistronic expression of E7. The monocistronic mRNA is not very abundant, but we have shown that an E7-luciferase fusion protein can be expressed in SiHa cells from a monocistronic HPV-16 transcript initiated at nt 542. The monocistronic mRNA expresses E7-luciferase more efficiently than the most abundant in vivo-like mRNA E6*IE7, initiated by P97 and spliced from nt 226 to 409. Furthermore, the translation initiation of E7 is most abundant from the monocistronic mRNA. We have also shown that the P542 promoter is downregulated by the transcription factor activator protein 4 (AP-4) and the differentiation-dependent factor hSkn-1a, both binding downstream of the transcription initiation site. In conclusion, we have found that P542 is a relatively weak promoter compared with P97 and may be downregulated in differentiated epithelial cells.
Glahder
Jacob A
JA
The DNA Tumour Virus Group, Institute of Molecular Pathology, The Protein Laboratory, University of Copenhagen, Panum Institute, Bldg 6.2, Blegdamsvej 3C, DK-2200 Copenhagen N, Denmark.
Hansen
Christina N
CN
The DNA Tumour Virus Group, Institute of Molecular Pathology, The Protein Laboratory, University of Copenhagen, Panum Institute, Bldg 6.2, Blegdamsvej 3C, DK-2200 Copenhagen N, Denmark.
Vinther
Jeppe
J
The DNA Tumour Virus Group, Institute of Molecular Pathology, The Protein Laboratory, University of Copenhagen, Panum Institute, Bldg 6.2, Blegdamsvej 3C, DK-2200 Copenhagen N, Denmark.
Madsen
Birger S
BS
The DNA Tumour Virus Group, Institute of Molecular Pathology, The Protein Laboratory, University of Copenhagen, Panum Institute, Bldg 6.2, Blegdamsvej 3C, DK-2200 Copenhagen N, Denmark.
Norrild
Bodil
B
The DNA Tumour Virus Group, Institute of Molecular Pathology, The Protein Laboratory, University of Copenhagen, Panum Institute, Bldg 6.2, Blegdamsvej 3C, DK-2200 Copenhagen N, Denmark.
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D008969:Molecular Sequence Data; D009856:Oncogene Proteins, Viral / Q000235:genetics* / Q000378:metabolism; D016366:Open Reading Frames; D027383:Papillomaviridae / Q000235:genetics* / Q000378:metabolism; D050725:Papillomavirus E7 Proteins; D011401:Promoter Regions, Genetic / Q000502:physiology*; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012333:RNA, Messenger; D012367:RNA, Viral; D012097:Repressor Proteins; D014157:Transcription Factors; C055473:enhancer-binding protein AP-4; C059731:oncogene protein E7, Human papillomavirus type 16