Evidence for an association between U1 RNA and interspersed repeat single-copy RNAs in the cytoplasm of sea urchin eggs†

Abstract

Psoralen crosslinking of RNA–RNA intermolecular duplexes in sea urchin egg extracts reveals that some maternal poly(A)⁺ RNA molecules are complexed with U1 RNA, a cofactor in somatic nuclear pre-mRNA splicing. Reaction of egg extracts with a monoclonal antibody specific for U1 snRNP selects, in addition to Ul, RNAs that contain repeated sequences interspersed with single-copy elements. Antibodyselection experiments with nucleate and anucleate egg halves demonstrate that most of the Ul RNA–inter-spersed RNA complexes are cytoplasmic, as is the egg’s store of total Ul snRNP. These results raise the possibility that maternal interspersed RNAs include unprocessed pre-messenger RNA molecules in arrested complexes with splicing cofactors.