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Publication Abstract from PubMed

Rnt1 endoribonuclease, the yeast homolog of RNAse III, plays an important role in the maturation of a diverse set of RNAs. The enzymatic activity requires a conserved catalytic domain, while RNA binding requires the double-stranded RNA-binding domain (dsRBD) at the C-terminus of the protein. While bacterial RNAse III enzymes cleave double-stranded RNA, Rnt1p specifically cleaves RNAs that possess short irregular stem-loops containing 12-14 base pairs interrupted by internal loops and bulges and capped by conserved AGNN tetraloops. Consistent with this substrate specificity, the isolated Rnt1p dsRBD and the 30-40 amino acids that follow bind to AGNN-containing stem-loops preferentially in vitro. In order to understand how Rnt1p recognizes its cognate processing sites, we have defined its minimal RNA-binding domain and determined its structure by solution NMR spectroscopy and X-ray crystallography. We observe a new carboxy-terminal helix following a canonical dsRBD structure. Removal of this helix reduces binding to Rnt1p substrates. The results suggest that this helix allows the Rnt1p dsRBD to bind to short RNA stem-loops by modulating the conformation of helix alpha1, a key RNA-recognition element of the dsRBD.

A new alpha-helical extension promotes RNA binding by the dsRBD of Rnt1p RNAse III.,Leulliot N, Quevillon-Cheruel S, Graille M, van Tilbeurgh H, Leeper TC, Godin KS, Edwards TE, Sigurdsson ST, Rozenkrants N, Nagel RJ, Ares M, Varani G EMBO J. 2004 Jul 7;23(13):2468-77. Epub 2004 Jun 10. PMID:15192703^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.