<p>High-risk type human papillomaviruses (HPVs) are associated with cancer. HPVs are strictly epitheliotropic and infect basal cell layers, establishing a life cycle strongly linked to the differentiation stage of the infected cells. The viral capsid late genes, L2 and L1, are only expressed in terminally differentiated epithelium. Late gene expression involves regulation of most gene processing events including transcription, splicing, polyadenylation, mRNA stability and translation. </p><p>Both L2 and L1 have elements present in the open reading frames (ORFs) negatively affecting mRNA levels and translation. The negative elements in L1 were mapped to the first 514 nucleotides, with the strongest inhibitory effect located in the first 129 nucleotides. The negative elements in the L2 sequence were concentrated in two locations on the gene. Both genes were mutated by changing the nucleotide sequence while retaining the amino acid sequence. Mutating the first 514 nucleotides in L1 deactivated the negative elements while the entire L2 gene had to be mutated to achieve the same result. The L2 protein was found to localise the L1 protein into a punctuated pattern in the nucleus.</p><p>In the HPV-16 genome the negative elements reside in regions important for regulation of polyadenylation and splicing, critical for late gene expression. By exchanging parts of the L2 gene in subgenomic constructs with the corresponding mutant sequence we show that certain features of the L2 elements direct splicing to the L1 splice acceptor, and also regulate the efficiency of the early polyadenylation site. Cumulative binding of hnRNP H to the L2 mRNA gradually increased polyadenylation efficiency. Most interestingly, hnRNP H levels were downregulated in more differentiated epithelial cells. </p><p>Elucidation of how expression of the immunogenic late proteins is regulated would be greatly beneficial in prevention and treatment of HPV infection and thereby cancer.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-4774 |
| Date | January 2005 |
| Creators | Öberg, Daniel |
| Publisher | Uppsala University, Department of Medical Biochemistry and Microbiology, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, 1651-6206 ; 4 |
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