The E7 Oncoprotein Is Translated from Spliced E6*I Transcripts in High-Risk Human Papillomavirus Type 16- or Type 18-Positive Cervical Cancer Cell Lines via Translation Reinitiation

• DOI: 10.1128/jvi.80.9.4249-4263.2006
• Publication Date: 2006-04-12T19:38:32Z
• Authors: Shuang Tang; Mingfang Tao; J. Philip McCoy; Zhi-Ming Zheng
• Keywords: Cell Nucleus; 0301 basic medicine; Human papillomavirus 16; Human papillomavirus 18; Transcription, Genetic; RNA Splicing; Retinoblastoma; Down-Regulation; Exons; Oncogene Proteins, Viral; Introns; Cell Line; 3. Good health; DNA-Binding Proteins; Repressor Proteins; 03 medical and health sciences; Risk Factors; Humans; Female; RNA, Messenger; Phosphorylation; RNA, Small Interfering; Peptide Chain Initiation, Translational

High-risk human papillomaviruses (HPVs) encode two viral oncoproteins, E6 and E7, from a single bicistronic pre-mRNA containing three exons introns. Retention of intron 1 in the coding region is essential for production full-length oncoprotein. However, splicing extremely efficient cervical cancer cells, leading to spliced transcript, E6*I, E6. Here, we investigated whether this might benefit E7 production. Using RNA interference as tool, targeted using small interfering RNAs (siRNAs) HPV-positive cell lines. At an effective low dose, siRNAs specifically suppressed expression but not expression, demonstrated by stabilization p53. at high doses HPV18 1-specific siRNA substantially reduced level 18E6*I mRNA lacking HeLa implying its nuclear silencing on before splicing. Two other targeting exon 2 regions HPV16 -18, which oncoprotein, E6*I mRNAs remarkable extent preferentially accumulation hypophosphorylated p105Rb cycle arrest, indicating that majority proteins are translational products mRNAs. This was confirmed transient transfection 293 cells: could be translated only open reading frame (ORF) distance-dependent matter upstream ORF translation reinitiation. The data thus provide direct evidence high-risk HPVs responsible