title: The oligomeric Rep protein of Mungbean yellow mosaic India virus (MYMIV) is a likely replicative helicase.
abstract: Geminiviruses replicate by rolling circle mode of replication (RCR) and the viral Rep protein initiates RCR by the site-specific nicking at a conserved nonamer (TAATATT downward arrow AC) sequence. The mechanism of subsequent steps of the replication process, e.g. helicase activity to drive fork-elongation, etc. has largely remained obscure. Here we show that Rep of a geminivirus, namely, Mungbean yellow mosaic India virus (MYMIV), acts as a replicative helicase. The Rep-helicase, requiring > or =6 nt space for its efficient activity, translocates in the 3'-->5' direction, and the presence of forked junction in the substrate does not influence the activity to any great extent. Rep forms a large oligomeric complex and the helicase activity is dependent on the oligomeric conformation ( approximately 24mer). The role of Rep as a replicative helicase has been demonstrated through ex vivo studies in Saccharomyces cerevisiae and in planta analyses in Nicotiana tabacum. We also establish that such helicase activity is not confined to the MYMIV system alone, but is also true with at least two other begomoviruses, viz., Mungbean yellow mosaic virus (MYMV) and Indian cassava mosaic virus (ICMV).
authors.affiliation: Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110 067, India.
authors.forename: Nirupam Roy
authors.initials: NR
authors.lastname: Choudhury
authors.forename: Punjab Singh
authors.initials: PS
authors.lastname: Malik
authors.forename: Dharmendra Kumar
authors.initials: DK
authors.lastname: Singh
authors.forename: Mohammad Nurul
authors.initials: MN
authors.lastname: Islam
authors.forename: Kosalai
authors.initials: K
authors.lastname: Kaliappan
authors.forename: Sunil Kumar
authors.initials: SK
authors.lastname: Mukherjee
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D053839:Begomovirus / Q000201:enzymology* / Q000235:genetics*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis; D017384:Sequence Deletion; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D004265:DNA Helicases