Transcription of repeated sequences of the mouse B1 family in friend erythroleukaemic cells: Intermolecular RNA-RNA duplex formation between polyadenylated and non-polyadenylated nuclear RNAs

Abstract

It has been shown by previous workers that heterogeneous nuclear RNA in eucaryotic cells exists in the form of a complex with small nuclear RNA molecules, which are involved in RNA processing. It is demonstrated in this report that polyadenylated RNAs from the nuclei of Friend erythroleukaemic cells are isolated as complexes with a wide spectrum of non-polyadenylated RNAs. The associated non-polyadenylated RNAs are mainly of high molecular weight (15 to 30 S), but include the 4.5 S and 7 S RNA species. The complexes can be disrupted by denaturation with dimethyl sulphoxide, but also can be reconstituted by reannealing under appropriate stringency conditions. Saturation experiments involving unique DNA probes have shown that the associated non-polyadenylated RNA has a high base sequence complexity. It is shown that complexes involving poly(A) + nuclear RNA contain transcripts of the highly repeated mouse B1 family. The vast majority of these repetitive sequence transcripts are removed by processing within the nucleus and are barely detectable in poly(A) + polysomal RNA. Double-stranded RNA prepared from the nuclear complexes by digestion with ribonucleases contains sequences complementary to the mouse B1 family, suggesting that these may be involved in duplex formation between polyadenylated and non-polyadenylated RNAs. The possible role of interrnolecular RNA-RNA duplexes involving repetitive sequences in the folding of messenger RNA precursors prior to removal of introns and splicing is discussed.