A calmodulin-related protein that suppresses posttranscriptional gene silencing in plants

Posttranscriptional gene silencing (PTGS) is an ancient eukaryotic regulato ry mechanism in which a particular RNA sequence is targeted and destroyed. The helper component-proteinase (HC-Pro) of plant potyviruses suppresses PT GS in plants; Using a yeast two-hybrid system, we identified a calmodulin-r elated protein (termed rgs-CaM) that interacts with HC-Pro. Here we report that rgs-CaM, like HC-Pro itself, suppresses gene silencing. Our work is th e first report identifying a cellular suppressor of PTGS.