title: Identification of an adeno-associated virus Rep protein binding site in the adenovirus E2a promoter.
abstract: Adeno-associated virus (AAV) and other parvoviruses inhibit proliferation of nonpermissive cells. The mechanism of this inhibition is not thoroughly understood. To learn how AAV interacts with host cells, we investigated AAV's interaction with adenovirus (Ad), AAV's most efficient helper virus. Coinfection with Ad and AAV results in an AAV-mediated inhibition of Ad5 gene expression and replication. The AAV replication proteins (Rep) activate and repress gene expression from AAV and heterologous transcription promoters. To investigate the role of Rep proteins in the suppression of Ad propagation, we performed chromatin immunoprecipitation analyses that demonstrated in vivo AAV Rep protein interaction with the Ad E2a gene promoter. In vitro binding of purified AAV Rep68 protein to the Ad E2a promoter was characterized by electrophoretic mobility shift assays (Kd= 200 +/- 25 nM). A 38 bp, Rep68-protected region (5'-TAAGAGTCAGCGCGCAGTATTTACTGAAGAGAGCCT-3') was identified by DNase I footprint analysis. The 38-bp protected region contains the weak E2a TATA box, sequence elements that resemble the Rep binding sites identified by random sequence oligonucleotide selection, and the transcription start site. These results suggest that Rep binding to the E2a promoter contributes to the inhibition of E2a gene expression from the Ad E2a promoter and may affect Ad replication.
authors.affiliation: Department of Biochemistry and Cancer Biology, Medical College of Ohio, Toledo, Ohio 43614-5804, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Casper
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Timpe
authors.forename: John David
authors.initials: JD
authors.lastname: Dignam
authors.forename: James P
authors.initials: JP
authors.lastname: Trempe
mesh_terms: D017502:Adenovirus E2 Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000260:Adenoviruses, Human / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000229:Dependovirus / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics* / Q000502:physiology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D017502:Adenovirus E2 Proteins; D004268:DNA-Binding Proteins; D014764:Viral Proteins; C068734:rep proteins, Adeno-associated virus 2