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PDBsum entry 1k6h
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References listed in PDB file
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Key reference
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Title
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Solution structure of conserved agnn tetraloops: insights into rnt1p RNA processing.
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Authors
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I.Lebars,
B.Lamontagne,
S.Yoshizawa,
S.Aboul-Elela,
D.Fourmy.
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Ref.
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EMBO J, 2001,
20,
7250-7258.
[DOI no: ]
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PubMed id
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Abstract
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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.
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Figure 1.
Figure 1 Illustration of Rnt1p model substrates. The conserved
AGNN nucleotides are shown in bold. The mutations introduced in
the wild-type sequence are shown in grey. The four heterologous
base pairs used to stabilize the structure are shown as an
outline. R31 represents the terminal stem -loop of the U5 snRNA.
R32 represents the terminal stem -loop of snR47. R31U is R31
with a mutation that changes the conserved A residue in the
tetraloop to U. R31A contains the R31 stem sequence but the loop
sequence is changed to GAAA. R31L contains the R31 sequence and
an insertion of 10 bp that extends the stem size to a total of
19 bp. The sites of cleavages by Rnt1p are indicated by the
arrowheads.
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Figure 6.
Figure 6 Stereo views of single representative structures of
AGUC (A) and AGAA (B) tetraloops. All heavy atoms are displayed.
Bases are coloured in light blue, with nitrogen and oxygen atoms
in dark blue and red, respectively. Ribose -phosphate backbones
are coloured in yellow, and phosphate oxygen in red.
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The above figures are
reprinted
from an Open Access publication published by Macmillan Publishers Ltd:
EMBO J
(2001,
20,
7250-7258)
copyright 2001.
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Headers
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