ACCUMULATION OF POLYADENYLATED MESSENGER-RNA DURING LIVER-REGENERATION

Cytoplasmic and polysomal poly(A)+-mRNA increased by 120% prior to the onset of DNA synthesis during the regeneration of rat liver following partial hepatectomy. Despite this large change in cytoplasmic mRNA and an approximately 50% increase in total nuclear RNA, the amount of polyadenylated nuclear RNA increased by only 15-20% during this time. Neither the average size of nuclear or of cytoplasmic polyadenylated mRNA nor the length of their poly(A) tracts changed during liver regeneration. Polysomal poly(A)+-mRNA increased proportionately more and at a faster rate than rRNA during the 1st day following partial hepatectomy. Normal livers contained a substantial proportion of cytoplasmic poly(A)+-mRNA not associated with polysomes but this proportion was not altered in 3 h regenerating liver. In regenerating liver most preexisting cytoplasmic mRNA does not appear to be recruited into polysomes prior to the substantial increase in the amount of cytoplasmic poly(A)+-mRNA.