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Two distinct recognition signals define the site of endonucleolytic cleavage at the 5'-end of yeast 18S rRNA.
- Source :
-
The EMBO journal [EMBO J] 1995 Oct 02; Vol. 14 (19), pp. 4883-92. - Publication Year :
- 1995
-
Abstract
- Three of the four eukaryotic ribosomal RNA molecules (18S, 5.8S and 25-28S rRNA) are transcribed as a single precursor, which is subsequently processed into the mature species by a complex series of cleavage and modification reactions. Early cleavage at site A1 generates the mature 5'-end of 18S rRNA. Mutational analyses have identified a number of upstream regions in the 5' external transcribed spacer (5' ETS), including a U3 binding site, which are required in cis for processing at A1. Nothing is known, however, about the requirement for cis-acting elements which define the position of the 5'-end of the 18S rRNA or of any other eukaryotic rRNA. We have introduced mutations around A1 and analyzed them in vivo in a genetic background where the mutant pre-rRNA is the only species synthesized. The results indicate that the mature 5'-end of 18S rRNA in yeast is identified by two partially independent recognition systems, both defining the same cleavage site. One mechanism identifies the site of cleavage at A1 in a sequence-specific manner involving recognition of phylogenetically conserved nucleotides immediately upstream of A1 in the 5' ETS. The second mechanism specifies the 5'-end of 18S rRNA by spacing the A1 cleavage at a fixed distance of 3 nt from the 5' stem-loop/pseudoknot structure located within the mature sequence. The 5' product of the A1 processing reaction can also be identified, showing that, in contrast to yeast 5.8S rRNA, the 5'-end of 18S rRNA is generated by endonucleolytic cleavage.
- Subjects :
- Base Sequence
Conserved Sequence
Molecular Sequence Data
Mutation
Nucleic Acid Conformation
RNA Precursors chemistry
RNA Precursors genetics
RNA Processing, Post-Transcriptional physiology
RNA, Ribosomal, 18S chemistry
RNA, Ribosomal, 18S genetics
Saccharomyces cerevisiae genetics
Endoribonucleases metabolism
RNA Precursors metabolism
RNA, Ribosomal, 18S metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0261-4189
- Volume :
- 14
- Issue :
- 19
- Database :
- MEDLINE
- Journal :
- The EMBO journal
- Publication Type :
- Academic Journal
- Accession number :
- 7588617
- Full Text :
- https://doi.org/10.1002/j.1460-2075.1995.tb00169.x