Author: Ann Marie MorenoPublisher:
ISBN:
Category :
Languages : en
Pages : 133
Book Description
In metazoans, the genes that code for the U6 small nuclear RNA (snRNA) have promoters that consist of a proximal sequence element (PSE) and a TATA box. The PSE is recognized by the multi-subunit small nuclear RNA activating protein complex (SNAPc). SNAPc forms a complex on the U6 promoter with TFIIIB, an RNA polymerase III-specific general transcription factor that includes TBP, Brf1 (Brf2 in vertebrates), and Bdp1. Here we show that, in the fruit fly Drosophila melanogaster, DmSNAPc directly recruits Bdp1 to the U6 promoter. We also demonstrate that an 87-residue region of Bdp1 is sufficient for this recruitment and is, furthermore, sufficient to recruit TBP to the TATA box. The non-conserved N-terminal tail of TBP also plays a role in stabilizing TBP incorporation into the DmSNAPc-Bdp1 complex. While Bdp1 recruitment by DmSNAPc is independent of the presence of TBP, Brf1, or a TATA box, it does require that DmSNAPc be bound to a U6 gene PSE rather than a PSE derived from a U1 gene (which is transcribed by RNA polymerase II). We also confirmed that Brf1 is present at U6 snRNA genes but not at U1 genes. These findings further develop the concept that DmSNAPc adopts different conformations upon binding U6 and U1 gene PSEs, and that these different DmSNAPc conformations lead to the subsequent recruitment of distinct general transcription factors and RNA polymerases for U6 and U1 gene transcription.
