title: High-affinity Rep-binding is not required for the replication of a geminivirus DNA and its satellite.
abstract: The 682-nt satellite DNA (sat-DNA) of Tomato leaf curl virus (TLCV) depends on the helper virus for its replication. In contrast to the strict specificity that exists in each geminivirus for its cognate replication associated protein (Rep), TLCV sat-DNA can utilize Rep encoded by distinct geminiviruses. We have used a combination of protein-binding assays and mutagenesis to show that repeat motifs in TLCV and sat-DNA are essential for Rep-binding in vitro. Surprisingly, mutants of TLCV and sat-DNA impaired in their ability to bind TLCV Rep in vitro were infectious in tomato. Thus, in contrast to other geminiviruses reported, TLCV and sat-DNA replication is independent of the high-affinity in vitro Rep binding. These results prompt a reassessment of the current model of geminivirus replication where Rep/DNA interaction is a highly specific step in the initiation of rolling circle replication.
authors.affiliation: Horticulture Unit, CSIRO Division of Plant Industry, Glen Osmond 5064, Adelaide, Australia.
authors.forename: Baochuan
authors.initials: B
authors.lastname: Lin
authors.forename: S A
authors.initials: SA
authors.lastname: Akbar Behjatnia
authors.forename: Ian B
authors.initials: IB
authors.lastname: Dry
authors.forename: John W
authors.initials: JW
authors.lastname: Randles
authors.forename: M Ali
authors.initials: MA
authors.lastname: Rezaian
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication; D004276:DNA, Satellite / Q000378:metabolism*; D004268:DNA-Binding Proteins; D017791:Geminiviridae / Q000235:genetics*; D018551:Solanum lycopersicum / Q000821:virology*; D008969:Molecular Sequence Data; D015534:Trans-Activators / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D004276:DNA, Satellite; D004268:DNA-Binding Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases