Solution structure of conserved AGNN tetraloops: insights into Rnt1p RNA processing.
Lebars, I., Lamontagne, B., Yoshizawa, S., Aboul-Elela, S., Fourmy, D.(2001) EMBO J 20: 7250-7258
- PubMed: 11743001 
- DOI: https://doi.org/10.1093/emboj/20.24.7250
- Primary Citation of Related Structures:  
1K6G, 1K6H - PubMed Abstract: 
Rnt1p, the yeast orthologue of RNase III, cleaves rRNAs, snRNAs and snoRNAs at a stem capped with conserved AGNN tetraloop. Here we show that 9 bp long stems ending with AGAA or AGUC tetraloops bind to Rnt1p and direct specific but sequence-independent RNA cleavage when provided with stems longer than 13 bp. The solution structures of these two tetraloops reveal a common fold for the terminal loop stabilized by non-canonical A-A or A-C pairs and extensive base stacking. The conserved nucleotides are stacked at the 5' side of the loop, exposing their Watson-Crick and Hoogsteen faces for recognition by Rnt1p. These results indicate that yeast RNase III recognizes the fold of a conserved single-stranded tetraloop to direct specific dsRNA cleavage.
Organizational Affiliation: 
Laboratoire de RMN, ICSN-CNRS, 1 ave de la terrasse, F-91190 Gif-sur-Yvette, France.