The Different Activities of the Two Activation Domains of the Brn-3a Transcription Factor Are Dependent on the Context of the Binding Site

Abstract

The POU (Pit-Oct-Unc) family transcription factor Brn-3a contains two distinct activation domains, one at the N terminus of the molecule and one at the C terminus coincident with the DNA binding domain. These different activation domains have been shown previously to differ in their ability to activate an artificial test promoter containing a Brn-3a binding site and the naturally occurring ␣-internexin gene promoter. Here we identify the target site for Brn-3a in the ␣-internexin gene promoter and show that it can confer responsiveness to Brn-3a on a heterologous promoter. One of the single-stranded DNA sequences derived from either this novel Brn-3a binding site or from the previously characterized site in the test promoter are shown to bind Brn-3a preferentially compared with the complementary single strand or the corresponding double-stranded sequence. The pattern of responsiveness of these two sequences when cloned upstream of the same test promoter and co-transfected with constructs encoding various portions of Brn-3a indicates that the activity of the two Brn-3a activation domains is dependent upon differences in the context of the target sequence in each promoter rather than on differences in the target sequence itself.The POU (Pit-Oct-Unc) family of transcription factors play a critical role in the regulation of gene expression in neuronal cells acting by binding to sequences related to the consensus octamer motif ATGCAAAT in the promoters of their target genes (for review, see Verrijzer and van der Vliet (1993) and Wegner et al. (1993)). The Brn-3 family of mammalian POU factors are of particular interest as the mammalian factors most closely related to the nematode POU protein Unc-86 whose inactivation results in the failure to develop specific neuronal cell types particularly sensory neurons (Desai et al., 1988;Finney et al., 1988). Three mammalian Brn-3 factors encoded by distinct genes exist (Theil et al., 1993 and are known as Brn-3a (also known as Brn-3.0: Gerrero et al., 1993;Lillycrop et al., 1992), Brn-3b (also known as Brn-3.2: Lillycrop et al., 1992;Turner et al., 1994), and Brn-3c (also known as Brn-3

C/EBP Factor Suppression of Inhibition of Type II Secreted Phospholipase A2 Promoter in HepG2 Cells: Possible Role of Single-Strand Binding Proteins

“…Many cloned SSBPs have very low affinities for double-stranded DNA (7,21,30,36,51), which is consistent with our data. The heterogeneous nuclear ribonucleoprotein K (hnRNP) (30), which binds to both RNA and single-stranded DNA, and some other SSBPs (18,21) all bind to CT-or C-rich sequences, but some other SSBPs bind to different sequences.…”

“…CArG boxes in the apoVLDL II promoter (51) and GXXXXG motif in the promoter of the TSH receptor (36) bind such activities. An octamer motif is recognized by two members of the POU family on the ␣-internexin promoter, one an activator and the second an inhibitor (7). The [Ϫ217; Ϫ204] region of the sPLA 2 promoter and the flanking sequences are not C or CT rich, and we can find no obvious feature in common with published SSBP binding sites except a GXXXXG motif between positions Ϫ210 and Ϫ205 (36).…”

“…Since inhibition of the [Ϫ326;ϩ20] sPLA 2 promoter was not affected by mutation of the binding sites of the previously characterized transcription factors but was removed by altering the [Ϫ217;Ϫ204] sequence at the junction of elements C and D which was not recognized by any double-strand binding protein, we looked for the involvement of SSBPs in the negative regulation of the sPLA 2 promoter. SSBPs inhibit the activities of several eukaryotic promoters (7,18,21,39,(51)(52)(53). The orientation and position of the DNA recognition sequence do not usually affect the regulatory activities of double-strand binding factors.…”

Caprin-1 is a target of the deafness genePou4f3and is recruited to stress granules in cochlear hair cells in response to ototoxic damage

“…Previously published Pou4f3 targets have all been upregulated, although not all are regulated through direct interaction with the target promoter (Clough et al, 2004;Hertzano et al, 2007;Hertzano et al, 2004). POU domain transcription factors have the ability to act as both repressors and activators of transcription, and can be influenced by interactions with cofactors (Budhram-Mahadeo et al, 1996;Dawson et al, 1996a;Dawson et al, 1996b;Phillips and Luisi, 2000), as well as by the spacing and context of response elements within the target promoter (Remenyi et al, 2002).…”

POU Transcription Factors Brn-3a and Brn-3b Interact with the Estrogen Receptor and Differentially Regulate Transcriptional Activity via an Estrogen Response Element

“…In addition, Brn-3a was found to be an activator of a reporter construct containing its binding site, while Brn-3b inhibited basal activity of this promoter (6, 48). Both proteins appear to recognize and bind to the same DNA sequence element in the double-stranded conformation (6,8,48) but were also capable of binding to single-stranded DNA. This was demonstrated by the preferential binding of both Brn-3a and Brn-3b to the antisense strand of the DNA binding site identified in the ␣-internexin promoter (8).…”