title: Analysis of the costructure of the simian virus 40 T-antigen origin binding domain with site I reveals a correlation between GAGGC spacing and spiral assembly.
abstract: Polyomavirus origins of replication contain multiple occurrences of G(A/G)GGC, the high-affinity binding element for the viral initiator T-antigen (T-ag). The site I regulatory region of simian virus 40, involved in the repression of transcription and the enhancement of DNA replication initiation, contains two GAGGC sequences arranged head to tail and separated by a 7-bp AT-rich sequence. We have solved a 3.2-Å costructure of the SV40 origin-binding domain (OBD) bound to site I. We have also established that T-ag assembly on site I is limited to the formation of a single hexamer. These observations have enabled an analysis of the role(s) of the OBDs bound to the site I pentanucleotides in hexamer formation. Of interest, they reveal a correlation between the OBDs bound to site I and a pair of OBD subunits in the previously described hexameric spiral structure. Based on these findings, we propose that spiral assembly is promoted by pentanucleotide pairs arranged in a head-to-tail manner. Finally, the possibility that spiral assembly by OBD subunits accounts for the heterogeneous distribution of pentanucleotides found in the origins of replication of polyomaviruses is discussed.
authors.affiliation: Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Gretchen
authors.initials: G
authors.lastname: Meinke
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Phelan
authors.forename: Celia J
authors.initials: CJ
authors.lastname: Harrison
authors.forename: Peter A
authors.initials: PA
authors.lastname: Bullock
mesh_terms: D000952:Antigens, Polyomavirus Transforming / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004261:DNA Replication; D004279:DNA, Viral / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D011485:Protein Binding; D055503:Protein Multimerization; D018741:Replication Origin / Q000235:genetics; D013539:Simian virus 40 / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D000952:Antigens, Polyomavirus Transforming; D004279:DNA, Viral; D004268:DNA-Binding Proteins