Oct-1 Preferentially Interacts with Androgen Receptor in a DNA-dependent Manner That Facilitates Recruitment of SRC-1

Abstract

Gene regulation by steroid hormone receptors depends on the particular character of the DNA response element, the array of neighboring transcription factors, and recruitment of coactivators that interface with the transcriptional machinery. We are studying these complex interactions for the androgen-dependent enhancer of the mouse sex-limited protein (Slp) gene. This enhancer has, in addition to multiple androgen receptor (AR)-binding sites, a central region (FPIV) with a binding site for the ubiquitous transcription factor Oct-1 that appears crucial for hormonal regulation in vivo. To examine the role of Oct-1 in androgen-specific gene activation, we tested the interaction of Oct-1 with AR versus glucocorticoid receptor (GR) in vivo and in vitro. Oct-1 coimmunoprecipitated from cell lysates with both AR and GR, but significant association with AR required both proteins to be DNA-bound. This was confirmed by sensitivity of the protein association to treatment with ethidium bromide or micrococcal nuclease. Addition of DNA to micrococcal nuclease-treated samples restored interaction, even when binding sites were on separate DNA molecules, suggesting association was due to direct protein-protein interaction and not indirect tethering via the DNA. AR/GR chimeras revealed that interaction of the N and C termini of AR was required to communicate the DNA-bound state that enhances interaction with Oct-1. Protease digestion assays of hormone-bound receptors revealed further conformational changes in the ligand binding domain of AR, but not GR, upon DNA binding. Furthermore, these conformational changes led to increased interaction with the coactivator SRC-1, via the NID 4 domain, suggesting DNA binding facilitates recruitment of SRC-1 by the AR-Oct-1 complex. Altogether, these results suggest that the precise arrangement of binding sites in the Slp enhancer ensures proper hormonal response by imposing differential interactions between receptors and Oct-1, which in turn contributes to SRC-1 recruitment to the promoter.

Intra-domain communication between the N-terminal and DNA-binding domains of the androgen receptor: modulation of androgen response element DNA binding

“…Robins and co-workers have argued that the selective response of the AR depends not only on the DNA architecture of the response sequence but the presence of non-receptor proteins and possible communication between receptor domains (see Gonzalez & Robins 2001, Grad et al 2001. The AR-NTD has previously been implicated in the AR-specific response of an internal exonic enhancer sequence, identified within the AR gene.…”

“…However, in addition to half-site recognition there is also evidence from DNA selection studies that nucleotides in the flanking and spacer sequences may also play a role in DNA binding and response element selection (Roche et al 1992, Nelson et al 1999. Moreover, investigation of the autoregulation of the AR gene by the receptor has shown that interactions with non-receptor proteins and/or communication between receptor domains are responsible for the AR-specific response (Gonzalez & Robins 2001, Grad et al 2001). …”

Cooperative Coactivation of Estrogen Receptor α in ZR-75 Human Breast Cancer Cells by SNURF and TATA-binding Protein

“…Two recent reports on enhanced NR coactivation by SRC-1 exhibit some similarities with our studies on SNURF-ER␣ interactions. Oct-1 interacts with the AR and enhances recruitment of SRC-1 and androgen response element-dependent promoter activity in COS-7 cells (98). However, these interactions are promoterspecific and require both AR and Oct-1 DNA binding sites.…”

Androgen receptor and prostate apoptosis response factor-4 target the c-FLIP gene to determine survival and apoptosis in the prostate gland

“…The molecular mechanisms of the action of these factors on AR-driven gene expression are largely unknown. Some factors, such as prostate epithelium-specific ETS transcription factor (PDEF) (Oettgen et al 2000) and octamer binding transcription factor (OCT)-1/2 (Prefontaine et al 1999, Gonzalez & Robins 2001, have sequence-specific DNA-binding activity and might synergistically interact with DNA in the presence of AR. It was also reported that c-jun interacted with the DBD of AR and inhibited AR-ARE interaction (Sato et al 1997).…”