Multiple ASF/SF2 sites in the human papillomavirus type 16 (HPV-16) E4-coding region promote splicing to the most commonly used 3'-splice site on the HPV-16 genome

J Virol. 2010 Aug;84(16):8219-30. doi: 10.1128/JVI.00462-10. Epub 2010 Jun 2.

Abstract

Our results presented here demonstrate that the most abundant human papillomavirus type 16 (HPV-16) mRNAs expressing the viral oncogenes E6 and E7 are regulated by cellular ASF/SF2, itself defined as a proto-oncogene and overexpressed in cervical cancer cells. We show that the most frequently used 3'-splice site on the HPV-16 genome, site SA3358, which is used to produce primarily E4, E6, and E7 mRNAs, is regulated by ASF/SF2. Splice site SA3358 is immediately followed by 15 potential binding sites for the splicing factor ASF/SF2. Recombinant ASF/SF2 binds to the cluster of ASF/SF2 sites. Mutational inactivation of all 15 sites abolished splicing to SA3358 and redirected splicing to the downstream-located, late 3'-splice site SA5639. Overexpression of a mutant ASF/SF2 protein that lacks the RS domain, also totally inhibited the usage of SA3358 and redirected splicing to the late 3'-splice site SA5639. The 15 ASF/SF2 binding sites could be replaced by an ASF/SF2-dependent, HIV-1-derived splicing enhancer named GAR. This enhancer was also inhibited by the mutant ASF/SF2 protein that lacks the RS domain. Finally, silencer RNA (siRNA)-mediated knockdown of ASF/SF2 caused a reduction in spliced HPV-16 mRNA levels. Taken together, our results demonstrate that the major HPV-16 3'-splice site SA3358 is dependent on ASF/SF2. SA3358 is used by the most abundantly expressed HPV-16 mRNAs, including those encoding E6 and E7. High levels of ASF/SF2 may therefore be a requirement for progression to cervical cancer. This is supported by our earlier findings that ASF/SF2 is overexpressed in high-grade cervical lesions and cervical cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Gene Expression Regulation, Viral*
  • HeLa Cells
  • Host-Pathogen Interactions*
  • Human papillomavirus 16 / physiology*
  • Humans
  • Molecular Sequence Data
  • Nuclear Proteins / metabolism*
  • Proto-Oncogene Mas
  • RNA Splice Sites*
  • RNA Splicing*
  • RNA, Viral / metabolism*
  • RNA-Binding Proteins
  • Serine-Arginine Splicing Factors

Substances

  • MAS1 protein, human
  • Nuclear Proteins
  • Proto-Oncogene Mas
  • RNA Splice Sites
  • RNA, Viral
  • RNA-Binding Proteins
  • Serine-Arginine Splicing Factors