title: A cyclin-binding motif in human papillomavirus type 18 (HPV18) E1^E4 is necessary for association with CDK-cyclin complexes and G2/M cell cycle arrest of keratinocytes, but is not required for differentiation-dependent viral genome amplification or L1 capsid protein expression.
abstract: The G2/M arrest function of human papillomavirus (HPV) E4 proteins is hypothesized to be necessary for viral genome amplification. Full-length HPV18 E1^E4 protein is essential for efficient viral genome amplification. Here we identify key determinants within a CDK-bipartite consensus recognition motif in HPV18 E1^E4 that are critical for association with active CDK-cyclin complexes and in vitro phosphorylation at the predicted CDK phosphorylation site (threonine 23). The optimal cyclin-binding sequence ((43)RRLL(46)) within this E4 motif is required for G2/M arrest of primary keratinocytes and correlates with cytoplasmic retention of cyclin B1, but not cyclin A. Disruption of this motif in the E4 ORF of HPV18 genomes, and the subsequent generation of stable cell lines in primary keratinocytes revealed that this motif was not essential for viral genome amplification or L1 capsid protein induction. We conclude that the HPV18 E4 G2/M arrest function does not play a role in early vegetative events.
authors.affiliation: Cancer Research UK Cancer Centre, School of Cancer Sciences, University of Birmingham, Birmingham, UK.
authors.forename: Gillian L
authors.initials: GL
authors.lastname: Knight
authors.forename: Alice G
authors.initials: AG
authors.lastname: Pugh
authors.forename: Emma
authors.initials: E
authors.lastname: Yates
authors.forename: Ian
authors.initials: I
authors.lastname: Bell
authors.forename: Regina
authors.initials: R
authors.lastname: Wilson
authors.forename: Cary A
authors.initials: CA
authors.lastname: Moody
authors.forename: Laimonis A
authors.initials: LA
authors.lastname: Laimins
authors.forename: Sally
authors.initials: S
authors.lastname: Roberts
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D036022:Capsid Proteins / Q000096:biosynthesis; D002453:Cell Cycle; D002478:Cells, Cultured; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism*; D052161:Human papillomavirus 18 / Q000235:genetics / Q000472:pathogenicity*; D006801:Humans; D015603:Keratinocytes / Q000502:physiology / Q000821:virology*; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D011485:Protein Binding; D037521:Virulence Factors / Q000378:metabolism; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins; D016213:Cyclins; D015514:Oncogene Proteins, Fusion; D037521:Virulence Factors; D018844:Cyclin-Dependent Kinases; C480565:L1 protein, Human papillomavirus type 18