Five to six percent (by mass) of AKR‐2B mouse embryo cell polysomal RNA consists of messenger RNA sequences which may exist in polyadenylated form. In the steady state, however, only 30–40% of these molecules are retained by extensive passage over oligo(dT)‐cellulose, the remainder being present in the form of poly(A)‐deficient analogues. Within experimental limits, these poly(A)‐deficient analogues contain representatives of all poly(A)‐containing mRNA sequences in these cells. An analysis of the kinetics of hybridization of cDNA probes enriched for either abundant or rare poly(A)‐containing mRNA sequences suggests that the frequency distributions of poly(A)‐containing and poly(A)‐deficient analogues are dissimilar, and that a relationship exists between the intracellular frequency of a given mRNA sequence and the number of poly(A)‐deficient analogues of that sequence. High frequency sequences appear to be enriched in the poly(A)‐containing fraction, while low frequency sequences are predominately associated with the poly(A)‐deficient fraction, thus, poly(A) may play a role in the regulation of mRNA frequency in the cytoplasm. Copyright © 1980 Wiley‐Liss, Inc.
