Activities associated with the putative replication initiation protein of Coconut foliar decay virus, a tentative member of the genus Nanovirus

National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE12618 Tallinn, Estonia 1 Institute of Biotechnology, Viikki Biocenter, University of Helsinki, PO Box 56, FIN-00014 Helsinki, Finland 2 Department of Virology and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia 3 Author for correspondence: Andres Merits (at the Viikki Biocenter). Fax +358 9 191959366. e-mail Merits{at}operoni.helsinki.fi The putative replication initiation protein (Rep) of Coconut foliar decay virus (CFDV) was expressed as a 6 x His recombinant protein in E. coli and in recombinant baculovirus. Purified 6 x His–Rep protein was demonstrated to possess sequence non-specific RNA- and ssDNA-binding activities as well as magnesium-dependent ATPase/GTPase activity. The yeast two-hybrid system revealed that CFDV Rep could interact with itself. Subcellular distribution of the CFDV Rep was studied by fractionation of insect cells infected with recombinant baculovirus expressing the 6 x His–Rep protein and by laser scanning confocal microscopy of Nicotiana benthamiana epidermal cells bombarded with a construct encoding CFDV Rep fused to GFP. It was shown that CFDV Rep associated predominantly with nuclei and membranes of infected/transfected cells. These activities of CFDV-encoded Rep are very similar to those reported for Reps of geminiviruses.