The oncornavirus maturation process: quantitative correlation between morphological changes and conversion of genomic virion RNA.

Avian myeloblastosis virus (AMV) was harvested at different time intervals from chick leukemic myeloblasts, and the rate of the maturation process of AMV was estimated on the basis of morphological changes in the virions and conversion of genomic viral RNA. The change from immature virions characterized by the presence of an electronlucent center to the condensed mature form (with dense nucleoid) was accompanied by the conversion of 30-40S RNA to 60S RNA. Both processes were quantitatively defined, correlated, and found to proceed in parallel at the same speed. Early stages of maturation were characterized by a high turnover of immature to mature virions; 31-40% of the mature forms were found in 3.5-min virus harvests. The rate of this process decreased with time. The 17-hour harvests still revealed the presence of 10-15% of immature virions. The course of the maturation process is discussed.