Interaction of Estrogen Receptor α with 3-Methyladenine DNA Glycosylase Modulates Transcription and DNA Repair

Abstract

Estrogen receptor ␣ (ER␣) interacts with basal transcription factors, coregulatory proteins, and chromatin modifiers to initiate transcription of the target genes. We have identified a novel interaction between ER␣ and the DNA repair protein 3-methyladenine DNA glycosylase (MPG) thereby providing a functional link between gene expression and DNA repair. Interestingly, the ER␣-MPG interaction was enhanced by the presence of estrogen response element (ERE)-containing DNA. In vitro pull-down assays indicated that the interaction of ER␣ with MPG was direct and occurred through the DNAand ligand-binding domains and the hinge region of the receptor. More importantly, endogenously expressed ER␣ and MPG from MCF-7 cells coimmunoprecipitated with ER␣-and MPG-specific antibodies. The ER␣-MPG interaction had functional consequences on the activities of both proteins. ER␣ increased MPG acetylation, stabilized the binding of MPG with hypoxanthine-containing oligos, and enhanced MPG-catalyzed removal of hypoxanthine from DNA. In turn, MPG dramatically stabilized the interaction of ER␣ with ERE-containing oligos, decreased p300-mediated acetylation of the receptor, and reduced transcription of simple and complex ERE-containing reporter plasmids in a dose-dependent manner. Our studies suggest that recruitment of MPG to ERE-containing genes influences transcription and plays a role in maintaining integrity of the genome by recruiting DNA repair proteins to actively transcribing DNA.Estrogen is critical for the growth, development, and homeostasis of neural, skeletal, cardiovascular, and reproductive tissues (1, 2). The actions of estrogen are mediated by two members of the nuclear receptor family, estrogen receptors (ERs) 1 ␣ and ␤. ER␣ is, however, generally a more potent transcriptional activator than ER␤ (3-5). Like other nuclear receptor family members, ER␣ has a modular structure. At the amino terminus is the A/B region with its autonomous activation function 1 (6). Region C encompasses the DNA binding domain and is linked by the hinge domain to region E, which contains the ligand-binding domain (LBD, Ref. 7). The DNAbinding domain has two zinc finger motifs that are involved in DNA binding. The LBD contains a hydrophobic pocket that interacts with estrogens and antiestrogens. The LBD also contains a ligand-dependent activation function 2, which is responsible for interaction of the receptor with coregulatory proteins (8 -10).ER␣ binds to estrogen response elements (EREs) in target genes to initiate changes in transcription. The consensus ERE is comprised of the palindromic sequence GGTCAnnnTGACC and is found in the Xenopus laevis vitellogenin A2 gene (11). In addition to interacting with EREs, ER␣ modulates transcription through its interaction with components of the basal transcription machinery, regulatory proteins, and chromatin modifiers (12). ER␣ interacts with proteins in the basal transcription complex including TATA-binding protein (13). The coregulatory proteins steroid receptor coactivator 1, transcription interm...

DEMETER and REPRESSOR OF SILENCING 1 encode 5-methylcytosine DNA glycosylases

“…A primary mechanism involves interactions with proteins that regulate transcription. It has been reported that methyl purine DNA glycosylase associates with the transcriptional repressor MBD1 to cooperatively inhibit gene expression (34), and 3-methyladenine DNA glycosylase interacts with estrogen receptor ␣ to modulate estrogen-mediated transcription (35). There is also evidence that TDG modulates transcription through interactions with hormone receptors (36, 37), transcription factors (38), and coactivators such as the CPB͞p300 acetylase complex (39).…”

An invariant aspartic acid in the DNA glycosylase domain of DEMETER is necessary for transcriptional activation of the imprinted MEDEA gene

“…Thymine DNA glycosylase has been reported to both activate and repress gene transcription by a variety of mechanisms, including binding to hormone receptors (29,30), interacting with transcription factors (31), and associating with CBP͞p300 acetylase, which remodels chromatin and activates transcription through histone acetyltransferase activity (32). Methylpurine DNA glycosylase has a synergistic effect on gene silencing by interacting with the methyl CpG-binding domain protein 1 (MBD1) transcriptional repressor (33) and 3-methyladenine DNA glycosylase interacts with estrogen receptor ␣ to inhibit gene transcription (34). Thus, DNA glycosylases are linked to the process of gene regulation by physical interactions that modulate the activities of transcription factors, receptors, and chromatin-remodeling proteins.…”

Interaction of the Tumor Metastasis Suppressor Nonmetastatic Protein 23 Homologue H1 and Estrogen Receptor α Alters Estrogen-Responsive Gene Expression

“…www.aacrjournals.org estrogen-responsive gene expression have been observed with other ERa-associated DNA repair proteins (14,22,29). It has been suggested that these proteins may help to stabilize the transcription complex so that DNA repair and transcription can occur simultaneously.…”

“…Interestingly, we have identified other DNA repair proteins, 3-methyladenine DNA glycosylase (MPG) and flap endonuclease (FEN-1), which associate with ERa and influence estrogenresponsive gene expression (22,29). Like NM23-H1, MPG and FEN-1 increase ERa-ERE binding in gel mobility shift assays and decrease transcription of a reporter plasmid in transient transfection assays.…”

“…Thus, although NM23-H1 was not present in the protein-DNA complex, it did increase the ERa-ERE interaction. The inability of coregulatory proteins to form a stable trimeric complex with the receptor and DNA in gel mobility shift assays has been reported previously by us and others (14,15,22,(26)(27)(28)(29) and may result from the transient interaction of NM23-H1 with the receptor-DNA complex, the necessity of other proteins to stabilize the receptor-DNA interaction, and/or the extended period of electrophoresis required for gel mobility shift assays.…”