Special Sm core complex functions in assembly of the U2 small nuclear ribonucleoprotein of Trypanosoma brucei.
The processing of polycistronic pre-mRNAs in trypanosomes requires the spliceosomal small ribonucleoprotein complexes (snRNPs) U1, U2, U4/U6, U5, and SL, each of which contains a core of seven Sm proteins. Recently we reported the first evidence for a core variation in spliceosomal snRNPs; specifically, in the trypanosome U2 snRNP, two of the canonical Sm proteins, SmB and SmD3, are replaced by two U2-specific Sm proteins, Sm15K and Sm16.5K. Here we identify the U2-specific, nuclear-localized U2B'' protein from Trypanosoma brucei. U2B'' interacts with a second U2 snRNP protein, U2-40K (U2A'), which in turn contacts the U2-specific Sm16.5K/15K subcomplex. Together they form a high-affinity, U2-specific binding complex. This trypanosome-specific assembly differs from the mammalian system and provides a functional role for the Sm core variation found in the trypanosomal U2 snRNP.
Preusser
Christian
C
Institute of Biochemistry, Justus Liebig University of Giessen, Germany.
Palfi
Zsofia
Z
Bindereif
Albrecht
A
D000595:Amino Acid Sequence; D000818:Animals; D008969:Molecular Sequence Data; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000235:genetics; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014346:Trypanosoma brucei brucei / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055517:snRNP Core Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D015800:Protozoan Proteins; D012342:RNA, Small Nuclear; D017413:Ribonucleoprotein, U2 Small Nuclear; C405484:U2 small nuclear RNA; C080405:U2 snRNP, Trypanosoma brucei; D055517:snRNP Core Proteins