INTER-MOLECULAR BASE-PAIRED INTERACTION BETWEEN COMPLEMENTARY SEQUENCES PRESENT NEAR THE 3' ENDS OF 5S RIBOSOMAL-RNA AND 18S(16S) RIBOSOMAL-RNA MIGHT BE INVOLVED IN THE REVERSIBLE ASSOCIATION OF RIBOSOMAL-SUBUNITS

Highly conserved sequences present at an identical position near the 3′ ends of eukaryotic and prokaryotic 5S rRNAs are complementary to the 5′ strand of the m62A hairpin structure near the 31 ends of 18S rRNA and 16S rRNA, respectively. The extent of base-pairing and the calculated stabilities of the hybrids that can be constructed between 5E rRNAs and the small ribosomal subunit RNAs are greater than most, if not all, RNA-RNA interactions that have been implicated in protein synthesis. The existence of complementary sequences in 5S rPNA and small ribo-somal subunit RNA, along with the previous observation that there is very efficient and selective hybridization in vitro between 5S and 18S rRNA, suggests that base-pairing Between 5S rRNA in the large ribosomal subunit and 18S(16S) rRNA in the small ribosomal subunit might be involved in the reversible association of ribosomal subunits. Structural and functional evidence supporting this hypothesis is discussed. © 1979 Information Retrieval Limited.