title: Dimerization of the human papillomavirus type 16 E2 N terminus results in DNA looping within the upstream regulatory region.
abstract: Papillomavirus E2 proteins play a central role in regulating viral gene expression and replication. DNA-binding activity is associated with the C-terminal domain of E2, which forms a stable dimer, while the N-terminal domain is responsible for E2's replication and transactivation functions. The crystal structure of the latter domain revealed a second dimerization interface on E2 which may be responsible for DNA loop formation in the regulatory region of the human papillomavirus (HPV) genome. We investigated the biological significance of the N-terminal dimerization by introducing single amino acid substitutions into the dimerization interface. As expected, these substitutions did not influence the C-terminal dimerization and DNA-binding functions of E2. However, the mutations led to reduced transactivation of a synthetic E2-responsive reporter gene, while HPV DNA replication was unaffected. The effect of the mutations on DNA looping was visualized by atomic force microscopy. While wild-type E2 was able to generate DNA loops, all three mutant E2 proteins were defective in this ability. Our results suggest that N-terminal dimerization plays a role in E2-mediated transactivation, probably via DNA looping, a common mechanism for remote regulation of gene transcription.
authors.affiliation: YCR Cancer Research Unit, Department of Biology (Area 13), University of York, Heslington, York, YO10 5DD United Kingdom.
authors.forename: Elena E
authors.initials: EE
authors.lastname: Hernandez-Ramon
authors.forename: Julie E
authors.initials: JE
authors.lastname: Burns
authors.forename: Wenke
authors.initials: W
authors.lastname: Zhang
authors.forename: Hannah F
authors.initials: HF
authors.lastname: Walker
authors.forename: Stephanie
authors.initials: S
authors.lastname: Allen
authors.forename: Alfred A
authors.initials: AA
authors.lastname: Antson
authors.forename: Norman J
authors.initials: NJ
authors.lastname: Maitland
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D019677:Artificial Gene Fusion; D002460:Cell Line; D004279:DNA, Viral / Q000378:metabolism / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D024202:Electrophoretic Mobility Shift Assay; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D052162:Human papillomavirus 16 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009856:Oncogene Proteins, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D015533:Transcriptional Activation; D014779:Virus Replication / Q000502:physiology*
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; C054855:E2 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins