Phosphorylation of the Bovine Papillomavirus E2 Protein on Tyrosine Regulates Its Transcription and Replication Functions.
Papillomaviruses are small, double-stranded DNA viruses that encode the E2 protein, which controls transcription, replication, and genome maintenance in infected cells. Posttranslational modifications (PTMs) affecting E2 function and stability have been demonstrated for multiple types of papillomaviruses. Here we describe the first phosphorylation event involving a conserved tyrosine (Y) in the bovine papillomavirus 1 (BPV-1) E2 protein at amino acid 102. While its phosphodeficient phenylalanine (F) mutant activated both transcription and replication in luciferase reporter assays, a mutant that may act as a phosphomimetic, with a Y102-to-glutamate (E) mutation, lost both activities. The E2 Y102F protein interacted with cellular E2-binding factors and the viral helicase E1; however, in contrast, the Y102E mutant associated with only a subset and was unable to bind to E1. While the Y102F mutant fully supported transient viral DNA replication, BPV genomes encoding this mutation as well as Y102E were not maintained as stable episomes in murine C127 cells. These data imply that phosphorylation at Y102 disrupts the helical fold of the N-terminal region of E2 and its interaction with key cellular and viral proteins. We hypothesize that the resulting inhibition of viral transcription and replication in basal epithelial cells prevents the development of a lytic infection.


OBJECTIVE
Papillomaviruses (PVs) are small, double-stranded DNA viruses that are responsible for cervical, oropharyngeal, and various genitourinary cancers. Although vaccines against the major oncogenic human PVs are available, there is no effective treatment for existing infections. One approach to better understand the viral replicative cycle, and potential therapies to target it, is to examine the posttranslational modification of viral proteins and its effect on function. Here we have discovered that the bovine papillomavirus 1 (BPV-1) transcription and replication regulator E2 is phosphorylated at residue Y102. While a phosphodeficient mutant at this site was fully functional, a phosphomimetic mutant displayed impaired transcription and replication activity as well as a lack of an association with certain E2-binding proteins. This study highlights the influence of posttranslational modifications on viral protein function and provides additional insight into the complex interplay between papillomaviruses and their hosts.
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Sara P
SP
Culleton
Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Sriramana
S
Kanginakudru
Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Marsha
M
DeSmet
Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Timra
T
Gilson
Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA.|General Hospital of PLA, Beijing, People's Republic of China.
Fang
F
Xie
Simmons Comprehensive Cancer Center and Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Shwu-Yuan
SY
Wu
Simmons Comprehensive Cancer Center and Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.|Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Cheng-Ming
CM
Chiang
Proteomics Core Facility, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Guihong
G
Qi
Proteomics Core Facility, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Mu
M
Wang
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA eandro@iu.edu.|Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Elliot J
http://orcid.org/0000-0002-8104-0703
EJ
Androphy
D052685:Alphapapillomavirus / Q000502:physiology; D000818:Animals; D052688:Bovine papillomavirus 1 / Q000502:physiology*; D002417:Cattle; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D016679:Genome, Viral; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D010766:Phosphorylation; D010957:Plasmids / Q000235:genetics; D011487:Protein Conformation; D021381:Protein Transport; D014158:Transcription, Genetic; D014443:Tyrosine / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
D004268:DNA-Binding Proteins; C051550:E2 protein, Bovine papillomavirus; D014764:Viral Proteins; D014443:Tyrosine
papillomavirus; papillomavirus E2; tyrosine phosphorylation; viral replication