Common design principles in the spliceosomal RNA helicase Brr2 and in the Hel308 DNA helicase.
Brr2 is a unique DExD/H box protein required for catalytic activation and disassembly of the spliceosome. It contains two tandem helicase cassettes that both comprise dual RecA-like domains and a noncanonical Sec63 unit. The latter may bestow the enzyme with unique properties. We have determined crystal structures of the C-terminal Sec63 unit of yeast Brr2, revealing three domains, two of which resemble functional modules of a DNA helicase, Hel308, despite lacking significant sequence similarity. This structural similarity together with sequence conservation between the enzymes throughout the RecA-like domains and a winged helix domain allowed us to devise a structural model of the N-terminal active cassette of Brr2. We consolidated the model by rational mutagenesis combined with splicing and U4/U6 di-snRNA unwinding assays, highlighting how the RecA-like domains and the Sec63 unit form a functional entity that appears suitable for unidirectional and processive RNA duplex unwinding during spliceosome activation and disassembly.
Pena
Vladimir
V
Abteilung Zelluläre Biochemie, Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, D-37077 Göttingen, Germany.
Jovin
Sina Mozaffari
SM
Fabrizio
Patrizia
P
Orlowski
Jerzy
J
Bujnicki
Janusz M
JM
Lührmann
Reinhard
R
Wahl
Markus C
MC
D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D020365:RNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017381:Spliceosomes / Q000201:enzymology*; D013329:Structure-Activity Relationship; D013997:Time Factors; D015003:Yeasts / Q000201:enzymology* / Q000235:genetics
D005656:Fungal Proteins; D012313:RNA; D004265:DNA Helicases; D020365:RNA Helicases