Abstract / Description of output
Cleavage of the yeast pre-rRNA at site A2 in internal transcribed spacer 1 (ITS1) requires multiple snoRNP species, whereas cleavage at site A3, located 72 nt 3' in ITS1, requires RNase MRP. Analyses of mutations in the pre-rRNA have revealed an unexpected link between processing at A2 and A3. Small substitution mutations in the 3' flanking sequence at A2 inhibit processing at site A3, whereas a small deletion at A3 has been shown to delay processing at site A2. Moreover, the combination of mutations in cis at both A2 and A3 leads to the synthesis of pre-rRNA species with 5' ends within the mature 18S rRNA sequence, at sites between +482 and +496. The simultaneous interference with an snoRNP processing complex at site A2 and an RNase MRP complex at site A3 may activate a pre-rRNA breakdown pathway. The same aberrant pre-rRNA species are observed in strains with mutations in the RNA component of RNase MRP, consistent with interactions between the processing complexes. Furthermore, genetic depletion of the snoRNA, snR30, has been shown to affect the coupling between cleavage by RNase MRP and subsequent exonuclease digestion. We conclude that an snoRNP-dependent processing complex that is required for A2 cleavage and that recognizes the 3' flanking sequence at A2, interacts with the RNase MRP complex bound to the pre-rRNA around site A3.
|Number of pages
|Published - 14 Nov 1996
Keywords / Materials (for Non-textual outputs)
- RNase MRP