Abstract / Description of output
Processing of the yeast pre-rRNA at site A2 in internal transcribed spacer 1 (ITS1) has been shown to require several small nucleolar ribonucleoprotein particles (snoRNPs) as trans-acting factors. Here we report a detailed mutational analysis of the cis-acting signals required to specify the site of A2 cleavage. Initial mutations established that the signals required for accurate cleavage of site A2 lie in the 3'-flanking sequence; deletion or substitution of nucleotides in this region strongly inhibits processing, and residual cleavage is inaccurate at the nucleotide level. In contrast, the deletion of the 5'-flanking nucleotides has no detectable effect on processing. An evolutionarily conserved sequence, ACAC, is located at the site of cleavage. Substitution of the 3' AC leads to heterogeneous cleavage, with activation of cleavage at an upstream ACAC sequence. In all mutants that retain an ACAC element, a site of cleavage is detected immediately 5' to this sequence, showing that this element is recognized. An ACAC sequence is, however, not essential for accurate cleavage of site A2. An additional signal is also present 3' to A2, in a region that has the potential to form a stem-loop structure that is evolutionarily conserved, but of low stability. As has been found for site A1 (the 5' end of the yeast 18S rRNA), the identification of the site of processing at A2 relies on multiple recognition elements.
|Number of pages
|Published - 14 Nov 1996
Keywords / Materials (for Non-textual outputs)
- RNA processing
- Saccharomyces cerevisiae