Comparison of the base-sequence complexities of polysomal and nuclear RNAs in growing Friend erythroleukemia cells

The base-sequence complexities of polysomal poly(A)+ RNA, nuclear poly(A)+ RNA, and total nuclear RNA from Friend erythroleukemia cells in logarithmic phase of growth were determined by measuring the proportion of labeled unique mouse DNA sequences which formed hybrids when incubated with a vast excess of each RNA. It was estimated that the RNAs had been transcribed from 1.8, 7.6, and 8.3%, respectively, of the haploid mouse genome. Although these estimates for polysomal and nuclear poly(A)+ RNAs were 2.5 times greater than those previously determined by analysis of the kinetics of the hybridization reactions between the RNAs and the cDNAs transcribed from them, they confirmed that the base-sequence complexity of nuclear poly(A)+ RNA in these cells is at least four times greater than that of polysomal poly(A)+ RNA.