IN-VITRO CLEAVAGE AND JOINING AT THE VIRAL ORIGIN OF REPLICATION BY THE REPLICATION INITIATOR PROTEIN OF TOMATO YELLOW LEAF CURL VIRUS

Replication of the single-stranded DNA genome of geminiviruses occurs via a double-stranded intermediate that is subsequently used as a temp late for rolling-circle replication of the viral strand, Only one of t he proteins encoded by the virus, here referred to as replication init iator protein (Rep protein), is indispensable for replication. We show that the Rep protein of tomato yellow leaf curl virus initiates viral -strand DNA synthesis by introducing a nick in the plus strand within the nonanucleotide (1)TAATATT down arrow (8)AC, identical among all ge miniviruses. After cleavage, the Rep protein remains bound to the 5' e nd of the cleaved strand. In addition, we show that the Rep protein ha s a joining activity, suggesting that it acts as a terminase, thus res olving the nascent viral single strand into genome-sized units,