Identification, characterization and crystal structure analysis of the human spliceosomal U5 snRNP-specific 15 kD protein.
The U5 small ribonucleoprotein particle (snRNP) contains various proteins involved in catalytic activities mediating conformational rearrangements of the spliceosome. We have isolated and characterized the evolutionarily highly conserved human U5 snRNP-specific protein U5-15kD. The crystal structure of U5-15kD determined at 1.4 A resolution revealed a thioredoxin-like fold and represents the first structure of a U5 snRNP-specific protein known so far. With respect to human thioredoxin the U5-15kD protein contains 37 additional residues causing structural changes which most likely form putative binding sites for other spliceosomal proteins or RNA. Moreover, a novel intramolecular disulfide bond replaces the canonical one found in the thioredoxin family. Even though U5-15kD appears to lack protein disulfide isomerase activity, it is strictly required for pre-mRNA splicing in vivo as we demonstrate by genetic depletion of its ortholog in Saccharomyces cerevisiae. Our data suggest that the previously reported involvement of its Schizosaccharomyces pombe ortholog Dim1p in cell cycle regulation is a consequence of its essential role in pre-mRNA splicing.
Reuter
K
K
Institut für Molekularbiologie und Tumorforschung, Universität Marburg, 35037, Germany.
Nottrott
S
S
Fabrizio
P
P
Lührmann
R
R
Ficner
R
R
D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012313:RNA / Q000378:metabolism; D012322:RNA Precursors / Q000235:genetics; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000235:genetics* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins; D013879:Thioredoxins / Q000737:chemistry
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D012322:RNA Precursors; D012333:RNA, Messenger; D017415:Ribonucleoprotein, U5 Small Nuclear; D029702:Schizosaccharomyces pombe Proteins; C118369:dim1 protein, S pombe; D013879:Thioredoxins; D012313:RNA