title: A noncanonical PWI domain in the N-terminal helicase-associated region of the spliceosomal Brr2 protein.
abstract: The spliceosomal RNA helicase Brr2 is required for the assembly of a catalytically active spliceosome on a messenger RNA precursor. Brr2 exhibits an unusual organization with tandem helicase units, each comprising dual RecA-like domains and a Sec63 homology unit, preceded by a more than 400-residue N-terminal helicase-associated region. Whereas recent crystal structures have provided insights into the molecular architecture and regulation of the Brr2 helicase region, little is known about the structural organization and function of its N-terminal part. Here, a near-atomic resolution crystal structure of a PWI-like domain that resides in the N-terminal region of Chaetomium thermophilum Brr2 is presented. CD spectroscopic studies suggested that this domain is conserved in the yeast and human Brr2 orthologues. Although canonical PWI domains act as low-specificity nucleic acid-binding domains, no significant affinity of the unusual PWI domain of Brr2 for a broad spectrum of DNAs and RNAs was detected in band-shift assays. Consistently, the C. thermophilum Brr2 PWI-like domain, in the conformation seen in the present crystal structure, lacks an expanded positively charged surface patch as observed in at least one canonical, nucleic acid-binding PWI domain. Instead, in a comprehensive yeast two-hybrid screen against human spliceosomal proteins, fragments of the N-terminal region of human Brr2 were found to interact with several other spliceosomal proteins. At least one of these interactions, with the Prp19 complex protein SPF27, depended on the presence of the PWI-like domain. The results suggest that the N-terminal region of Brr2 serves as a versatile protein-protein interaction platform in the spliceosome and that some interactions require or are reinforced by the PWI-like domain.
authors: Laboratory of Structural Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.
authors: Eva
authors: E
authors: Absmeier
authors: Laboratory of Structural Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.
authors: Leonie
authors: L
authors: Rosenberger
authors: Molecular Interaction Networks, Max-Planck-Institut für Molekulare Genetik, Ihnestrasse 63-73, 14195 Berlin, Germany.
authors: Luise
authors: L
authors: Apelt
authors: Laboratory of Structural Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.
authors: Christian
authors: C
authors: Becke
authors: Laboratory of Structural Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.
authors: Karine F
authors: KF
authors: Santos
authors: Molecular Interaction Networks, Max-Planck-Institut für Molekulare Genetik, Ihnestrasse 63-73, 14195 Berlin, Germany.
authors: Ulrich
authors: U
authors: Stelzl
authors: Laboratory of Structural Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.
authors: Markus C
authors: MC
authors: Wahl
mesh_terms: D000595:Amino Acid Sequence; D002597:Chaetomium / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D060066:Protein Interaction Maps; D020365:RNA Helicases / Q000737:chemistry / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017381:Spliceosomes / Q000737:chemistry / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D017411:Ribonucleoproteins, Small Nuclear; C545711:SNRNP200 protein, human; D029701:Saccharomyces cerevisiae Proteins; C104158:BRR2 protein, S cerevisiae; D020365:RNA Helicases
keywords: Brr2 RNA helicase; PWI domain; pre-mRNA splicing; protein–protein interactions; spliceosome