IN-VITRO ASSEMBLY OF POLIOVIRUSES .I. KINETICS OF ASSEMBLY OF EMPTY CAPSIDS AND ROLE OF EXTRACTS FROM INFECTED CELLS

The kinetics of the in vitro assembly of 14 S particles into 73 S empty capsids was studied in cytoplasmic extracts made from poliovirus-infected HeLa cells. The formation of 73 S particles is complete after 10-15 minutes at 37°. About 20% of the 14 S material appears to be defective. An attempt was made to identify the component(s) in infected cell extracts that are responsible for the assembly activity by testing its sensitivity to various agents. Extracts treated with sufficient ribonuclease to destroy the cell ribosomes are able to assemble 73 S particles from 14 S particles. Pretreatment of the extracts with metabolic poisons (NaCN, NaF) or inhibitors of protein synthesis has no affect on assembly activity. The assembly activity of extracts is inactivated by 50° for 20 minutes or pretreatment with trypsin or deoxycholate. Extracts in which the endogenous 14 S to 73 S assembly has been completed by preincubation retain their ability to assemble newly added 14 S particles. © 1969.