28 S ribosomal RNA in vertebrates. Locations of large-scale features revealed by electron microscopy in relation to other features of the sequences.
The 28 S rRNA from several vertebrate species, when examined by electron microscopy, is seen to contain regions of extensive secondary structure, as first reported for HeLa-cell 28 S rRNA by Wellauer & Dawid [(1973) Proc. Natl. Acad. Sci. U.S.A. 70, 2827-2831]. Here we correlate the locations of these regions, determined from the electron-microscopic data, with the primary structure of 28 S rRNA from human, mouse and Xenopus laevis determined by sequence analysis of rDNA. The secondary-structure features observed by electron microscopy correspond closely to phylogenetically variable G + C-rich regions that largely comprise the eukaryotic expansion segments in these three species. In most if not all cases the features can be identified with long G + C-rich helices deduced from sequence data. Correlations are given between the locations of the secondary-structure features and several 'landmark' restriction sites in 28 S rDNA. By correlating the locations of the rRNA methyl groups reported elsewhere [Maden (1988) J. Mol. Biol. 201, 289-314] with the present findings it is concluded that the rRNA secondary-structure features revealed by electron microscopy are largely or wholly unmethylated.
Wakeman
J A
JA
Department of Biochemistry, University of Liverpool, U.K.
Maden
B E
BE
D000818:Animals; D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004275:DNA, Ribosomal; D006801:Humans; D008745:Methylation; D051379:Mice; D008854:Microscopy, Electron; D012335:RNA, Ribosomal / Q000378:metabolism; D012339:RNA, Ribosomal, 28S / Q000378:metabolism; D014714:Vertebrates / Q000378:metabolism*; D014982:Xenopus laevis
D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D012339:RNA, Ribosomal, 28S; D004262:DNA Restriction Enzymes