Redundant cooperative interactions for assembly of a human U6 transcription initiation complex.
The core human U6 promoter consists of a proximal sequence element (PSE) located upstream of a TATA box. The PSE is recognized by the snRNA-activating protein complex (SNAP(c)), which consists of five types of subunits, SNAP190, SNAP50, SNAP45, SNAP43, and SNAP19. The TATA box is recognized by TATA box binding protein (TBP). In addition, basal U6 transcription requires the SANT domain protein Bdp1 and the transcription factor IIB-related factor Brf2. SNAP(c) and mini-SNAP(c), which consists of just SNAP43, SNAP50, and the N-terminal third of SNAP190, bind cooperatively with TBP to the core U6 promoter. By generating complexes smaller than mini-SNAP(c), we have identified a 50-amino-acid region within SNAP190 that is (i) required for cooperative binding with TBP in the context of mini-SNAP(c) and (ii) sufficient for cooperative binding with TBP when fused to a heterologous DNA binding domain. We show that derivatives of mini-SNAP(c) lacking this region are active for transcription and that with such complexes, TBP can still be recruited to the U6 promoter through cooperative interactions with Brf2. Our results identify complexes smaller than mini-SNAP(c) that are transcriptionally active and show that there are at least two redundant mechanisms to stably recruit TBP to the U6 transcription initiation complex.
Ma
Beicong
B
Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
Hernandez
Nouria
N
D004247:DNA / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D021122:Protein Subunits; D012342:RNA, Small Nuclear / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016385:TATA Box; D035181:TATA-Box Binding Protein / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D024363:Transcription Initiation Site; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D046911:Macromolecular Substances; D021122:Protein Subunits; D012342:RNA, Small Nuclear; D011993:Recombinant Fusion Proteins; D035181:TATA-Box Binding Protein; D014157:Transcription Factors; C405486:U6 small nuclear RNA; D004247:DNA