The minor coat protein of beet yellows closterovirus encapsidates the 5 ' terminus of RNA in virions

Filamentous particles of beet yellows closterovirus (BYV) are built of two related capsid proteins, of which the minor species, p24, forms a 75 nm tai l at one end of the virion. In the present work, we used polyclonal antibod ies against p24 for isolating the 'tailed' virion segments from sonicated B YV particle preparations. The [gamma-P-32]ATP-labelled RNA obtained from th e antibody-selected particle segments consistently showed stronger hybridiz ation with the 5'-terminal BYV cDNA clones than with the 3'-terminal cDNA c lones. These data clearly indicate that it is the 5'-terminal portion of th e closterovirus RNA genome that is encapsidated by p24.