Message sequences are not adjacent to poly(A) in heterogeneous nuclear RNA of Friend leukemic cells

Hybridization of labeled RNA with excess amounts of unlabeled complementary DNA (cDNA) was used to investigate the location of cytoplasmic mRNA sequences in heterogenous nuclear RNA (hnRNA) of noninduced Friend leukemic cells. A heterologous hybrid between hnRNA and cytoplasmic cDNA was formed. Two homologous hybrids were also formed, one between poly(A)-containing mRNA and cytoplasmic cDNA, and the other between poly-(A)-containing hnRNA and nuclear cDNA. All hybrids were selected on hydroxyapatite columns after RNase treatment. The hybrids were further investigated for the presence of poly(A). No poly(A) was found in the heterologous hybrid, while both homologous hybrids contained poly(A). From these results we conclude that there exists a spacer nucleotide sequence between the poly(A) and the message sequences in hnRNA.