Title: |
Automated extraction and classification of RNA tertiary structure cyclic
motifs Sebastien Lemieux and Francois Major, Nucleic Acids Research |
Speaker: |
Zhichuan Zhang
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Abstract |
A minimum cycle basis of the tertiary structure of a large ribosomal
subunit (LSU) X-ray crystal structure was analyzed. Most cycles are small,
as they are composed of 3- to 5 nt, and repeated across the LSU tertiary
structure. We used hierarchical clustering to quantify and classify the 4
nt cycles. One class is defined by the GNRA tetraloop motif. The
inspection of the GNRA class revealed peculiar instances in sequence.
First is the presence of UA, CA, UC and CC base pairs that substitute the
usual sheared GA base pair. Second is the revelation of GNR(Xn)A
tetraloops, where Xn is bulged out of the classical GNRA structure, and of
GN/RA formed by the two strands of interior-loops. We were able to
unambiguously characterize the cycle classes using base stacking and base
pairing annotations. The cycles identified correspond to small and cyclic
motifs that compose most of the LSU RNA tertiary structure and contribute
to its thermodynamic stability. Consequently, the RNA minimum cycles could
well be used as the basic elements of RNA tertiary structure prediction
methods.
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