The 3'-terminal sequence of mitochondrial 13S ribosomal RNA

The 3'-terminal sequence of the small subunit ribosomal RNA from hamster mitochondria

The 220 3'-terminal nucleotides of the small ribosomal subunit RNA (13S) of hamster (BHK-21) cell mitochondria have been sequenced and the positions of post-transcriptionally methylated residues within this sequence have been established. Also, we have derived the secondary structure of the 3'-terminus of mitochondrial 13S rRNA by 1) searching nucleotide sequences of 13S rRNA, procaryotic 16S rRNA and eucaryotic 18S rRNA for common secondary structures and 2) using single-strand specific endonucleases to map secondary interactions in 13S rRNA. The pyrimidine tract CCUCC in E. coli 16S rRNA, which participates in base-pairing with bacterial mRNA, is absent in mitochondrial 13S rRNA. We believe that the binding of mRNA to mammalian mitochondrial ribosomes is not mediated by a conventional Shine-Dalgarno interaction.

Complete nucleotide sequence of the 5' noncoding region of rabbit beta-globin mRNA

The 5' noncoding region sequence of rabbit beta-globin mRNA has been determined. This region is 53 nucleotides long, not including the A-U-G initiator sequence or m7Gppp "cap" structure. 32P-labeled DNA complementary to the 5' noncoding region was synthesized using reverse transcriptase with the synthetic deoxyoctanucleotide d(G-C-A-C-C-A-T-T) as a "primer". The cDNA produced was then sequenced using a modification of the gel-sequencing technique previously developed for DNA sequencing (G.G. Brownlee and E.M. Cartwright, manuscript in preparation). The sequence obtained was checked by depurination and nearest-neighbor analysis. The known sequence at the 3' end of rabbit 18S ribosomal RNA cannot base-pair extensively with the 5' noncoding region of beta-globin mRNA; however, it does form 6 base pairs around the initiation codon.