Related Experiment Videos
Mechanism of translation of the bicistronic mRNA encoding human papillomavirus type 16 E6-E7 genes
T M Tan1, B Gloss, H U Bernard
1Institute of Molecular and Cell Biology, National University of Singapore.
Abstract:
The transforming genes E6 and E7 of human papillomavirus (HPV) type 16 and other HPV types are expressed from a bicistronic mRNA with a characteristic spacing of 3 to 6 bp between the termination codon of E6 and the initiation codon of E7. Plasmid pSP64E6E7 which contains the reading frames of both E6 and E7 was constructed in order to study the expression of both proteins in a coupled transcription/rabbit reticulocyte translation system. Both E6 and E7 proteins were expressed simultaneously. This translation could be interfered with by antisense oligonucleotides corresponding to various regions of the transcript. Antisense oligonucleotides targeted at sequences flanking either side of the translation initiation codon of the E6 open reading frame were effective in inhibiting the synthesis of both proteins, whereas oligonucleotides complementary to the coding regions downstream of the first start codon showed either a considerably reduced effect or none at all. In particular, there was limited inhibition of E7 translation by antisense oligonucleotides flanking the translation start region of the E7 gene. In the presence of RNase H, it was possible to selectively inhibit the synthesis of either E6 or E7 by several gene-internal antisense oligonucleotides. We conclude that HPV16 E6-E7 bicistronic mRNA is fully functional and that both proteins are translated with equal efficiency via the scanning mechanisms with reinitiation at the second open reading frame. In addition, both AE6 and AE7 may have therapeutical potential as they are capable of inhibiting the proliferation of CaSki cells which contain the HPV16 genome.
Insights
Human papillomavirus (HPV) type 16 E6 and E7 proteins are efficiently produced from a single mRNA. Antisense oligonucleotides targeting these HPV genes show therapeutic potential by inhibiting cancer cell proliferation.
Area of Science:
- Molecular Biology
- Virology
- Oncology
Background:
- Human papillomavirus (HPV) type 16 oncogenes E6 and E7 are expressed from a bicistronic mRNA.
- A small intercistronic region (3-6 bp) exists between the E6 stop and E7 start codons.
Purpose of the Study:
- To investigate the expression mechanism of the HPV16 E6-E7 bicistronic mRNA.
- To assess the efficacy of antisense oligonucleotides in inhibiting E6 and E7 protein synthesis and their therapeutic potential.
Main Methods:
- Construction of plasmid pSP64E6E7 for coupled transcription/translation.
- Application of antisense oligonucleotides targeting various regions of the HPV16 E6-E7 transcript.
- Utilized RNase H for selective inhibition of protein synthesis.
- Assessed inhibition of CaSki cell proliferation.
Main Results:
- Both E6 and E7 proteins were simultaneously expressed from the bicistronic mRNA.
- Antisense oligonucleotides targeting the E6 initiation codon effectively inhibited both E6 and E7 synthesis.
- Limited inhibition of E7 was observed with antisense oligonucleotides targeting its specific start region.
- Selective inhibition of E6 or E7 synthesis was achieved using gene-internal antisense oligonucleotides with RNase H.
- Both AE6 and AE7 demonstrated inhibition of CaSki cell proliferation.
Conclusions:
- The HPV16 E6-E7 bicistronic mRNA is functional, with both proteins efficiently translated via scanning and reinitiation.
- Antisense oligonucleotides targeting HPV16 E6 and E7 show promise as a therapeutic strategy against HPV-associated cancers.