Nucleic Acids Research, Vol 25, Issue 8 1565-1569, Copyright © 1997 by Oxford University Press
I Kim, Y Muto, M Inoue, S Watanabe, A Kitamura, S Yokoyama, K Hosono, H Takaku, A Ono, M Kainosho, H Sakamoto and Y Shimura
It has been reported that a 183 residue fragment, consisting of the two
RNA-binding domains (RBD1- RBD2) of the Drosophila melanogster Sex- lethal
(Sxl) protein, strongly binds an oligonucleotide of the target RNA sequence
(5'-GUUUUUUUUC-3') that regulates alternative splicing, and forms four or
five hydrogen bonds with the imino groups of the RNA. In the present study,
we used site-directed mutagenesis to improve the solubility of the didomain
fragment of Sxl, and confirmed that this mutant fragment forms hydrogen
bonds with the target RNA in the same manner as that of the wild-type
fragment. The mutant fragment was shown to bind the cognate RNA sequences
GUUUUUUUUC and AUUUUUUUUC more tightly than UUUUUUUUC. By using a
[3-15N]uridine phosphoramidite, we synthesized a series of15N-labeled
target RNAs, in which one of the uridine residues was specifically replaced
by [3-15N]uridine. By observing the imino1H-15N coupling of the labeled
uridine residue, we assigned all four of the hydrogen-bonded imino protons
to U1, U2, U5 and U6, respectively, of the target RNA. The imino protons of
U2 and U6 exhibited nuclear Overhauser effects with aliphatic protons of
the protein. All these results indicate that the A/G, U1, U2, U5 and U6
residues in the target sequence of (G/A)UUUUUUUU are specifically
recognized by the two RNA-binding domains of the Sxl protein.
ARTICLES
NMR analysis of the hydrogen bonding interactions of the RNA-binding domains of the Drosophila sex-lethal protein with target RNA fragments with site-specific [3-15N]uridine substitutions
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan.
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