Co-existence of non-histone messenger RNA species lacking and containing polyadenylic acid in sea urchin embryos

The non-histone messenger RNAs of sea urchin embryos have been separated on oligo(T)-cellulose into fractions containing poly(A) and those entirely lacking poly(A). Proof of the existence of the class of mRNA lacking poly(A) is afforded by the following demonstrations: (1) the pulse-labeled RNA analyzed is bound to polyribosomes and has no non-polysomal contamination, (ii) The methods of extraction, as tested by mixing experiments between cytoplasmic extracts of sea urchin embryo and mammalian tissue culture cells, preclude partial degradation of mRNA containing poly(A) to yield artifactual species lacking poly(A), (iii) The non-histone mRNA lacking poly(A) has a mean sedimentation coefficient of 22 S, as measured in a denaturing solvent. It is shown not to consist of molecular aggregates of the putative histone 9 S mRNA, and its base composition differs markedly from those of both 9 S and ribosomal RNA, but resembles closely that of poly(A)-containing mRNA. (iv) Although the non-histone mRNAs lacking and containing poly(A) have similar base compositions and sizes (approximately 22 S), they differ widely in their nucleotide sequences. Complementary DNA, prepared with reverse transcriptase instructed by poly(A)-containing mRNA, hybridized to a negligible extent with RNA lacking poly(A).