The poly(A)(+)RNA sequence complexity is also represented in poly(A)(-)RNA in sea-urchin embryos.

The extent to which the poly(A)(+)RNA sequence complexity from sea-urchin embryos is also represented in poly(A)(-)RNA was determined by cDNA cross-hybridization. Eighty percent or more of both the cytoplasmic poly(A)(+)RNA and polysomal poly(A)(+)RNA sequences appeared in a poly(A)(-) form. In both cases, the cellular concentrations of the poly(A)(-)RNA molecules that reacted with the cDNA were similar to the concentrations of the homologous poly(A)(+) sequences. Additionally, few, if any, abundant poly(A)(+)mRNA molecules were quantitatively discriminated by polyadenylation, since the abundant poly(A)(+)sequences were also abundant in poly(A)(-)RNA. Neither degradation nor inefficient binding to oligo (dT)-cellulose can account for the observed cross-reactivity. These data indicate that, in sea-urchin embryos, the poly(A) does not regulate the utilization of mRNA by demarcating an mRNA subset that is specifically and completely polyadenylated.