Effect of cell proliferation on levels and diversity of poly(A)-containing mRNA.

The relationship between cell proliferation and the amount and diversity of polyribosome-associated poly(A)-containing messenger RNA [poly(A)+mRNA]has been investigated using a cloned AKR-mouse embryo cell culture system. The following results were obtained. First, an early response to the stimulation of proliferation of AKR-2B cells in culture is a rapid increase in the rate of accumulation of polyribosomal poly(A)+ mRNA. This results in a large increase in the total poly(A)+ mRNA content of rapidly proliferating cells compared to that found in resting cells. Second, the total amount of unique DNA sequence contributing to the poly(A)+ mRNA populations of both growing and resting cells is not detectably different. This corresponds to 9000-11,000 diverse gene equivalents of DNA and represents the transcription of 0.8-0.9% of the haploid mouse genome. Third, most of the increased poly(A)+ mRNA content of growing cells (greater than 90%) reflects an increased rate of production of polysomal mRNA species which are also found in resting cells. Fourth, growing cells appear to contain some species of poly(A)+ mRNA which are either absent or present in very low concentrations in non-growing cells. Within the limits of detection, however, all species of poly(A)+ mRNA present in non-growing cells are also present in growing cells.