Estrogen Receptor-related Receptor α1 Interacts with Coactivator and Constitutively Activates the Estrogen Response Elements of the Human Lactoferrin Gene

Abstract

The human estrogen receptor-related receptor (ERR␣1, NR3B1a) was shown to bind a steroidogenic factor binding element (SFRE), TCAAGGTCATC, 26 base pairs upstream from the estrogen response element (ERE) of the human lactoferrin gene promoter. A mutation made at SFRE significantly reduced estrogen-dependent transcription from the lactoferrin ERE in human endometrial cells. In this study, we demonstrated that ERR␣1 binds both SFRE and ERE elements and constitutively transactivates the lactoferrin gene promoter. In DNase I footprinting protection analysis, both SFRE and ERE regions were protected by glutathione S-transferase-ERR␣1 fusion protein. The receptor formed two protein-DNA complexes with either SFRE or ERE in electrophoresis mobility shift assay. Homodimerization of ERR␣1 was confirmed with the mammalian two-hybrid system. ERR␣1 activates reporter constructs containing various types of estrogen response elements in endometrial and non-endometrial cells in transient transfection experiments. Overexpressing the coactivator, SRC1a or GRIP1, further enhances ERR␣1-induced transcriptional activity. We demonstrated that the AF2 domain of ERR␣1 is essential for the transactivation function and that deletion or mutation at this region abrogates the activation capability. Protein-protein interaction between the SRC1a and ERR␣1 C terminus was confirmed with a GST glutathione S-transferase "pull-down" assay. When comparing ERR␣1 and the estrogen receptor ␣ (ER␣) in many of the experiments, we found that ER␣ can also bind SFRE of the lactoferrin gene and transactivate the promoter activity in a ligand-dependent manner. The present study demonstrated that ERR␣1 binds similar DNA elements as ER␣ and confers its transactivation function constitutively. Therefore, ERR␣1 may actively modulate the estrogen response of lactoferrin gene as well as other estrogen-responsive genes.

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

“…However, it is not present in the mammary cell lines studied here (data not shown). SRC-1 and SRC-3/AIB1 have also been shown to stimulate ERRa1 activity in transient transfection assays in some mammalian cell lines, albeit only modestly (15,16). Thus, GRIP1 is likely the major, physiologically relevant coactivator of ERRa1 in mammary cells.…”

“…GRIP1 has been shown to recognize the nuclear receptor box within the COOH terminus of ERRa1, enhancing transcriptional activity (16). Why, then, did GRIP1 fail to significantly enhance ERRa1 transcriptional activity in MCF-7 cells (Fig.…”

“…ERRa1 interacts with peroxisome proliferator-activated receptor coactivator-1a (13,14) and the p160 family of coactivators, including glucocorticoid receptor interacting protein 1 (GRIP1/SRC2; ref. 15), via a carboxyl-terminal coactivator-binding inverted LxLxxL motif (16). Bulky amino acid side chains almost completely fill the ERRa1 putative ligand-binding pocket (14,17), with residue Phe 329 recapitulating interactions analogous to ones provided by ligands, thereby promoting binding of coactivators (17).…”

Identification of estrogen-responsive genes based on the DNA binding properties of estrogen receptors using high-throughput sequencing technology

“…However, among them, only a small number have been shown to possess functional EREs within the transcription regulatory region. In mammals, these genes include transcription factors, such as JUN [32] , FOS [33] , PGR [34] , and TP53 [35] , intracellular signaling molecules, such as HRAS [36] , BCL2 [37] , and BRCA1 [38] , enzymes, such as CHAT [39] , NQO1 [40] , and CKB [41] , secreted proteins, such as LTF [42] , SCGB1A1 [43] , OVGP1 [44] , C3 [45] , and AGT [46] , hormones, such as LHB [47] , OXT [48] , PRL [49] , and AVP [50] , membrane proteins, such as SNAT2 [51] and VEGFA [52] , the motogen TFF1 [53] , and the protease CTSD [54] . These genes are assumed to directly mediate various estrogen actions in normal tissues, as well as in cancer and other diseases.…”

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

“…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). In contrast, however, the ERRs are not ligand-dependent but are constitutively active (36 -38) and are able to modulate many ER-regulated physiological pathways and ER target genes (29, 35, 39 -41).…”