The SNAP45 subunit of the small nuclear RNA (snRNA) activating protein complex is required for RNA polymerase II and III snRNA gene transcription and interacts with the TATA box binding protein.
The RNA polymerase II and III small nuclear RNA (snRNA) promoters contain a common basal promoter element, the proximal sequence element (PSE). The PSE binds a multisubunit complex we refer to as the snRNA activating protein complex (SNAPc). At least four polypeptides are visible in purified SNAPc preparations, which migrate with apparent molecular masses of 43, 45, 50, and 190 kDa on SDS/polyacrylamide gels. In addition, purified preparations of SNAPc contain variable amounts of TATA box binding protein (TBP). An important question is whether the PSEs of RNA polymerase II and III snRNA promoters recruit the exact same SNAP complex or slightly different versions of SNAPc, differing, for example, by the presence or absence of a subunit. To address this question, we are isolating cDNAs encoding different subunits of SNAPc. We have previously isolated the cDNA encoding the 43-kDa subunit SNAP43. We now report the isolation of the cDNA that encodes the p45 polypeptide. Antibodies directed against p45 retard the mobility of the SNAPc-PSE complex in an electrophoretic mobility shift assay, indicating that p45 is indeed part of SNAPc. We therefore refer to this protein as SNAP45. SNAP45 is exceptionally proline-rich, interacts strongly with TBP, and, like SNAP43, is required for both RNA polymerase II and III transcription of snRNA genes.
Sadowski
C L
CL
Cold Spring Harbor Laboratory, NY, USA.
Henry
R W
RW
Kobayashi
R
R
Hernandez
N
N
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000378:metabolism*; D012320:RNA Polymerase III / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000096:biosynthesis*; D016601:RNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism*; D016385:TATA Box; D035181:TATA-Box Binding Protein; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D012342:RNA, Small Nuclear; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D017411:Ribonucleoproteins, Small Nuclear; C099437:SNAPC2 protein, human; D035181:TATA-Box Binding Protein; D014157:Transcription Factors; D012319:RNA Polymerase II; D012320:RNA Polymerase III