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Two distinct recognition signals define the site of endonucleolytic cleavage at the 5'-end of yeast 18S rRNA.

Authors :
Venema J
Henry Y
Tollervey D
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.

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