title: DNA helicase activity is associated with the replication initiator protein rep of tomato yellow leaf curl geminivirus.
abstract: The Rep protein of tomato yellow leaf curl Sardinia virus (TYLCSV), a single-stranded DNA virus of plants, is the replication initiator essential for virus replication. TYLCSV Rep has been classified among ATPases associated with various cellular activities (AAA+ ATPases), in superfamily 3 of small DNA and RNA virus replication initiators whose paradigmatic member is simian virus 40 large T antigen. Members of this family are DNA- or RNA-dependent ATPases with helicase activity necessary for viral replication. Another distinctive feature of AAA+ ATPases is their quaternary structure, often composed of hexameric rings. TYLCSV Rep has ATPase activity, but the helicase activity, which is instrumental in further characterization of the mechanism of rolling-circle replication used by geminiviruses, has been a longstanding question. We present results showing that TYLCSV Rep lacking the 121 N-terminal amino acids has helicase activity comparable to that of the other helicases: requirements for a 3' overhang and 3'-to-5' polarity of unwinding, with some distinct features and with a minimal AAA+ ATPase domain. We also show that the helicase activity is dependent on the oligomeric state of the protein.
authors.affiliation: Institut des Sciences du Végétal, CNRS, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France.
authors.forename: Danielle
authors.initials: D
authors.lastname: Clérot
authors.forename: Françoise
authors.initials: F
authors.lastname: Bernardi
mesh_terms: D000595:Amino Acid Sequence; D053839:Begomovirus / Q000502:physiology*; D004265:DNA Helicases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology; D004279:DNA, Viral / Q000378:metabolism*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017384:Sequence Deletion; D014764:Viral Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins; C080288:replication protein AL1, Begomovirus; D004265:DNA Helicases