Factors determining the site of synthesis of poliovirus proteins: the early attachment of virus particles to endoplasmic membranes.

Cytoplasmic extracts of HeLa cells made 1 to 2 h after infection with radioactive poliovirus contained 150-s virus particles and 130-s, perhaps partially disrupted, particles. The latter were resistant to RNase but sensitive to dodecylsulphate. Both particles were associated with fast sedimenting material from which they could be released by deoxycholate, but not by EDTA. In isopyenic gradients of sucrose in DSO the labelled particles formed a sharp band coincident with membrane-bound ribosomes at a density of 1-23 g cm". It is suggested that attachment of virus particles to endoplasmic reticulum may be an early stage in the infectious cycle, determining the site of subsequent steps. The inhibition of cellular protein synthesis that develops during infection affects membranebound as well as free polysomes and therefore does not determine the membrane-association of viral protein synthesis.