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Solution Structure of the Second RNA Recognition Motif (RRM) Domain of Murine T Cell Intracellular Antigen-1 (TIA-1) and Its RNA Recognition Mode

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posted on 17.06.2008, 00:00 authored by Kanako Kuwasako, Mari Takahashi, Naoya Tochio, Chikage Abe, Kengo Tsuda, Makoto Inoue, Takaho Terada, Mikako Shirouzu, Naohiro Kobayashi, Takanori Kigawa, Seiichi Taguchi, Akiko Tanaka, Yoshihide Hayashizaki, Peter Güntert, Yutaka Muto, Shigeyuki Yokoyama
T cell intracellular antigen-1 (TIA-1), an apoptosis promoting factor, functions as a splicing regulator for the Fas pre-mRNA. TIA-1 possesses three RNA recognition motifs (RRMs) and a glutamine-rich domain. The second RRM (RRM2) is necessary and sufficient for tight, sequence-specific binding to the uridine-rich sequences buried around the 5′ splice sites. In the present study, we solved the solution structure of the murine TIA-1 RRM2 by heteronuclear−nuclear magnetic resonance spectroscopy. The TIA-1 RRM2 adopts the RRM fold (βαββαβ) and possesses an extra β-strand between β2 and β3, which forms an additional β-sheet with the C-terminal part of β2. We refer to this structure as the β2-β2′ β-loop. Interestingly, this characteristic β-loop structure is conserved among a number of RRMs, including the U2AF65 RRM2 and the Sex-lethal RRM1 and RRM2, which also bind to uridine-rich RNAs. Furthermore, we identified a new sequence motif in the β2-β2′ β-loop, the DxxT motif. Chemical shift perturbation analyses of both the main and side chains upon binding to the uridine pentamer RNA revealed that most of the β-sheet surface, including the β2-β2′ β-loop, is involved in the RNA binding. An investigation of the chemical shift perturbation revealed similarity in the RNA recognition modes between the TIA-1 and U2AF65 RRMs.

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