Study of Some Stages of Poliovirus Morphogenesis in MiO Cells

Abstract

Five to seven minutes after addition of 14 C-amino acids to poliovirus-infected MiO cells, radioactivity is found only in 5 S virus-specific structures. With increased time of labeling, radioactivity appears in considerable amounts also in the 14 S area. In the presence of guanidine blocking the transition of 14 S particles in subsequent structures in MiO cells, radioactivity is first detected in the 5 S zone and then accumulates predominantly in 14 S particles. These results indicate that formation of 5 S particles and conversion of a part of their protein into 14 S particles reflect the earliest stages of the morphogenesis of poliovirus. In contrast to poliovirus-infected HeLa cells, no 73 S particles could be detected in MiO cells, nor could 73 S structures be detected in poliovirus-infected MiO cells after a short incubation period (20 to 30 min) with radioactive amino acids, although formation of 150 S virions was observed. Addition of guanidine to infected MiO cells leads to accumulation of 14 S particles; however, 73 S particles are not detected. After removal of guanidine, radioactivity increases only in the 150 S area. Incubation of 14 S particles isolated from the sucrose gradient of the cytoplasmic extract of infected MiO cells resulted in formation of 73 S particles. The results obtained show the modification of the late stages of poliovirus morphogenesis in MiO cells.