Epidermal Growth Factor–Induced Signaling in Breast Cancer Cells Results in Selective Target Gene Activation by Orphan Nuclear Receptor Estrogen-Related Receptor α

Abstract

The orphan nuclear hormone receptor estrogen-related receptor A (ERRA, NR3B1) is a constitutive transcription factor that is structurally and functionally related to the classic estrogen receptors. ERRA can recognize both the estrogen response element and its own binding site (ERRE) in either dimeric or monomeric forms. ERRA is also a phosphoprotein whose expression in human breast tumors correlates with that of the receptor tyrosine kinase ErbB2, suggesting that its transcriptional activity could be regulated by signaling cascades. Here, we investigated growth factor regulation of ERRA function and found that it is phosphorylated in MCF-7 breast cancer cells in response to epidermal growth factor (EGF), an event that enhances its DNA binding. Interestingly, treatment with alkaline phosphatase shifts ERRA from a dimeric to a monomeric DNA-binding factor, and only the dimeric form interacts with the coactivator PGC-1A. In vitro, the DNA-binding domain of ERRA is selectively phosphorylated by protein kinase CD (PKCD), which increases its DNA-binding activity, whereas expression of constitutively active PKCD enhances TFF1 promoter activity via the ERRE. However, whereas treatment of MCF-7 cells with the phorbol ester phorbol-12-myristate 13-acetate also enhances ERRA activation of the TFF1 promoter reporter, it does not affect ERRA activity on its own promoter. In agreement, chromatin immunoprecipitation analysis shows that ERRA and RNA polymerase II are preferentially recruited to the TFF1 promoter after EGF treatment, whereas recruitment of these factors to its own promoter is not affected. These results reveal a mechanism through which growth factor signaling can selectively activate ERRA target genes in breast cancer cells. (Cancer Res 2005; 65(14): 6120-29)

Estrogen-Related Receptor α1 Transcriptional Activities Are Regulated in Part via the ErbB2/HER2 Signaling Pathway

“…The lower amount of phospo-labeled ERRa1 observed in the 4D5-treated cells was due to this treatment being inhibitory to cell growth (data not shown). Thus, we confirmed prior reports that ERRa1 is a phosphoprotein (9,38). We also conclude that ERRa1 was phosphorylated in vivo at several sites, with the extent of phosphorylation being cell type dependent and reduced by disruption of the ErbB2 signaling pathway.…”

“…Effects of E 2 on Expression of ERRa in MCF-7 and BT-474 Cells ERRa1 can either repress or activate ERE-regulated expression (8), a target sequence to which it binds exclusively as a homodimer (38). Given our finding that ERRa mRNA levels positively correlate with those of ErbB2 and ErbB3 (11), we speculated that posttranslational modifications mediated by the ErbB2-directed pathway might contribute to regulation of ERRa1 activities.…”

“…2B and C)? Barry et al (10) have reported that the exact sequence of the nine-nucleotide extended half-site sequence and the state of phosphorylation of ERRa1 (38) affect whether ERRa1 preferentially binds to an ERRE as a monomer or homodimer; ERRa1 acts as a repressor when bound as a monomer because it cannot recruit coactivators such as PGC-1a. However, the transcriptional activity of ERRa1 and its ability to recruit the coactivator GRIP1 to an ERE was shown here to be dependent on cell type (Fig.…”

Estrogen Induces Estrogen-related Receptor α Gene Expression and Chromatin Structural Changes in Estrogen Receptor (ER)-positive and ER-negative Breast Cancer Cells

“…Phosphorylated ERR␣ binds DNA and interacts with co-activators more efficiently. Therefore, it is possible that ERR␣ enhances its own expression through autoregulation (30,33).…”

“…ERR␣ is ubiquitous among tissues of the developing embryo and adult (20 -22) and regulates an assortment of genes and physiological processes (23)(24)(25)(26). Like the ERs, ERR␣ binds to EREs but is capable of also binding an estrogen-related response element (ERRE) unique to the ERRs (27)(28)(29) in monomer or dimer form (30). Once bound to DNA, ERR␣ recruits co-regulators similar to those recruited by the ERs and thereby influences gene expression, indicating a considerable degree of functional conservation between the ERs and ERRs (31)(32)(33)(34)(35).…”