A 57-nucleotide upstream early polyadenylation element in human papillomavirus type 16 interacts with hFip1, CstF-64, hnRNP C1/C2, and polypyrimidine tract binding protein.
We have investigated the role of the human papillomavirus type 16 (HPV-16) early untranslated region (3' UTR) in HPV-16 gene expression. We found that deletion of the early 3' UTR reduced the utilization of the early polyadenylation signal and, as a consequence, resulted in read-through into the late region and production of late L1 and L2 mRNAs. Deletion of the U-rich 3' half of the early 3' UTR had a similar effect, demonstrating that the 57-nucleotide U-rich region acted as an enhancing upstream element on the early polyadenylation signal. In accordance with this, the newly identified hFip1 protein, which has been shown to enhance polyadenylation through U-rich upstream elements, interacted specifically with the HPV-16 upstream element. This upstream element also interacted specifically with CstF-64, hnRNP C1/C2, and polypyrimidine tract binding protein, suggesting that these factors were either enhancing or regulating polyadenylation at the HPV-16 early polyadenylation signal. Mutational inactivation of the early polyadenylation signal also resulted in increased late mRNA production. However, the effect was reduced by the activation of upstream cryptic polyadenylation signals, demonstrating the presence of additional strong RNA elements downstream of the early polyadenylation signal that direct cleavage and polyadenylation to this region of the HPV-16 genome. In addition, we identified a 3' splice site at genomic position 742 in the early region with the potential to produce E1 and E4 mRNAs on which the E1 and E4 open reading frames are preceded only by the suboptimal E6 AUG. These mRNAs would therefore be more efficiently translated into E1 and E4 than previously described HPV-16 E1 and E4 mRNAs on which E1 and E4 are preceded by both E6 and E7 AUGs.
Zhao
Xiaomin
X
Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
Oberg
Daniel
D
Rush
Margaret
M
Fay
Joanna
J
Lambkin
Helen
H
Schwartz
Stefan
S
D020413:3' Untranslated Regions; D039241:Cleavage Stimulation Factor; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C / Q000378:metabolism*; D006801:Humans; D027383:Papillomaviridae / Q000235:genetics*; D026723:Polyadenylation; D038941:Polypyrimidine Tract-Binding Protein / Q000378:metabolism*; D011485:Protein Binding; D039104:RNA 3' Polyadenylation Signals; D012326:RNA Splicing; D012367:RNA, Viral / Q000096:biosynthesis / Q000235:genetics; D016601:RNA-Binding Proteins / Q000378:metabolism*; D017384:Sequence Deletion; D014158:Transcription, Genetic; D039221:mRNA Cleavage and Polyadenylation Factors / Q000378:metabolism*
D020413:3' Untranslated Regions; C474466:CSTF2T protein, human; D039241:Cleavage Stimulation Factor; C479818:FIP1L1 protein, human; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; D038941:Polypyrimidine Tract-Binding Protein