title: CCCTC-binding factor recruitment to the early region of the human papillomavirus 18 genome regulates viral oncogene expression.
abstract: Host cell differentiation-dependent regulation of human papillomavirus (HPV) gene expression is required for productive infection. The host cell CCCTC-binding factor (CTCF) functions in genome-wide chromatin organization and gene regulation. We have identified a conserved CTCF binding site in the E2 open reading frame of high-risk HPV types. Using organotypic raft cultures of primary human keratinocytes containing high-risk HPV18 genomes, we show that CTCF recruitment to this conserved site regulates viral gene expression in differentiating epithelia. Mutation of the CTCF binding site increases the expression of the viral oncoproteins E6 and E7 and promotes host cell proliferation. Loss of CTCF binding results in a reduction of a specific alternatively spliced transcript expressed from the early gene region concomitant with an increase in the abundance of unspliced early transcripts. We conclude that high-risk HPV types have evolved to recruit CTCF to the early gene region to control the balance and complexity of splicing events that regulate viral oncoprotein expression.
  
  
  OBJECTIVE
  The establishment and maintenance of HPV infection in undifferentiated basal cells of the squamous epithelia requires the activation of a subset of viral genes, termed early genes. The differentiation of infected cells initiates the expression of the late viral transcripts, allowing completion of the virus life cycle. This tightly controlled balance of differentiation-dependent viral gene expression allows the virus to stimulate cellular proliferation to support viral genome replication with minimal activation of the host immune response, promoting virus productivity. Alternative splicing of viral mRNAs further increases the complexity of viral gene expression. In this study, we show that the essential host cell protein CTCF, which functions in genome-wide chromatin organization and gene regulation, is recruited to the HPV genome and plays an essential role in the regulation of early viral gene expression and transcript processing. These data highlight a novel virus-host interaction important for HPV pathogenicity.
authors.affiliation: University of St. Andrews, School of Medicine, St. Andrews, Fife, United Kingdom.
authors.forename: Christian
authors.initials: C
authors.lastname: Paris
authors.affiliation: University of Birmingham, School of Cancer Sciences, Birmingham, United Kingdom.
authors.forename: Ieisha
authors.initials: I
authors.lastname: Pentland
authors.affiliation: University of Cambridge, Department of Pathology, Cambridge, United Kingdom.
authors.forename: Ian
authors.initials: I
authors.lastname: Groves
authors.affiliation: University of St. Andrews, School of Medicine, St. Andrews, Fife, United Kingdom.
authors.forename: David C
authors.initials: DC
authors.lastname: Roberts
authors.affiliation: University of St. Andrews, School of Medicine, St. Andrews, Fife, United Kingdom.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Powis
authors.affiliation: University of Cambridge, Department of Pathology, Cambridge, United Kingdom.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Coleman
authors.affiliation: University of Birmingham, School of Cancer Sciences, Birmingham, United Kingdom S.Roberts@bham.ac.uk j.l.parish@bham.ac.uk.
authors.forename: Sally
authors.initials: S
authors.lastname: Roberts
authors.affiliation: University of Birmingham, School of Cancer Sciences, Birmingham, United Kingdom S.Roberts@bham.ac.uk j.l.parish@bham.ac.uk.
authors.forename: Joanna L
authors.initials: JL
authors.lastname: Parish
mesh_terms: D001665:Binding Sites; D000076246:CCCTC-Binding Factor; D002478:Cells, Cultured; D004279:DNA, Viral / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D015870:Gene Expression; D015967:Gene Expression Regulation, Viral; D054884:Host-Pathogen Interactions; D052161:Human papillomavirus 18 / Q000502:physiology*; D006801:Humans; D015603:Keratinocytes / Q000821:virology; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis*; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*
chemical_list: D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C052603:E6 protein, Human papillomavirus type 18; C052633:E7 protein, Human papillomavirus type 18; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins