The metazoan-specific type 3 promoters, which are exemplified by the human U6 promoter, recruit a complex variously called the snRNA activating protein complex (SNAPc) (Sadowski et al., 1993), the PSE binding protein (PBP) (Waldschmidt et al., 1991), or the PSE transcription factor (PTF) (Murphy et al., 1992). The complex contains five types of subunits and binds to the PSE. Type 3 promoters also recruit Brf2-TFIIIB through a combination of protein-protein contacts with SNAPc and a direct association of the TBP component of Brf2-TFIIIB with the TATA box. This then allows RNA polymerase III to join the complex.
The down stream element (DSE) of type 3 promoters, which enhances transcription from the core promoter, almost invariably contains an octamer sequence and an SPH element (also called NONOCT element)(Cheung et al., 1993; Danzeiser et al., 1993; Kunkel et al., 1996; Myslinski et al., 1992). The octamer sequence recruits the POU domain protein Oct-1 (Herr et al., 1988; Sturm et al., 1988), and the SPH element recruits a zinc finger protein known as Staf or SPH binding factor (SBF), which has been cloned from humans (Myslinski et al., 1998; Rincon et al., 1998).
|2853685||Activation of the U2 snRNA promoter by the octamer motif defines a new class of RNA polymerase II enhancer elements||Genes Dev||1988|
|8336708||Functional characterization of elements in a human U6 small nuclear RNA gene distal control region||Mol Cell Biol||1993|
|8979085||Identification of a SPH element in the distal region of a human U6 small nuclear RNA gene promoter and characterization of the SPH binding factor in HeLa cell extracts||Gene Expr||1996|
|1868835||Identification of transcription factors required for the expression of mammalian U6 genes in vitro||EMBO J||1991|
|9776743||Molecular cloning of a cDNA encoding human SPH-binding factor, a conserved protein that binds to the enhancer-like region of the U6 small nuclear RNA gene promoter||Nucleic Acids Res||1998|
|1535687||Oct-1 and Oct-2 potentiate functional interactions of a transcription factor with the proximal sequence element of small nuclear RNA genes||Mol Cell Biol||1992|
|8339931||Targeting TBP to a non-TATA box cis-regulatory element: a TBP-containing complex activates transcription from snRNA promoters through the PSE||Genes Dev||1993|
|2905684||The ubiquitous octamer-binding protein Oct-1 contains a POU domain with a homeo box subdomain||Genes Dev||1988|
|9705341||ZNF76 and ZNF143 are two human homologs of the transcriptional activator Staf||J Biol Chem||1998|