Identification of an N-terminal domain of the plum pox potyvirus CI RNA helicase involved in self-interaction in a yeast two-hybrid system

Potyvirus CI RNA helicase is a protein involved in RNA genome replication a nd virus movement. The protein aggregates in the cytoplasm of infected cell s to form typical cylindrical inclusions. A yeast two-hybrid system was use d to analyse interactions of: the CI RNA helicase from plum pox potyvirus ( PPV) with itself and with other viral proteins. No interactions could be de tected of full-length CI protein with itself or with PPV P3/6K1, Nla, Nlb o r CP proteins. However, positive self-interactions were detected for N-term inal fragments of the CI protein, allowing the mapping of a CI-CI binding d omain to the N-terminal 177 aa of the protein. Further deletion analysis su ggested that several regions of this domain contribute to the interaction. Moreover, pull-down experiments demonstrate that, at least in vitro, full-l ength PPV CI protein is able to self-interact in the absence of other virus or plant factors.