Mixed lineage leukemia histone methylases play critical roles in estrogen‐mediated regulation of HOXC13

Abstract

HOXC13, a homeobox‐containing gene, is involved in hair development and human leukemia. The regulatory mechanism that drives HOXC13 expression is mostly unknown. Our studies have demonstrated that HOXC13 is transcriptionally activated by the steroid hormone estrogen (17β‐estradiol; E2). The HOXC13 promoter contains several estrogen‐response elements (EREs), including ERE1 and ERE2, which are close to the transcription start site, and are associated with E2‐mediated activation of HOXC13. Knockdown of the estrogen receptors (ERs) ERα and ERβ suppressed E2‐mediated activation of HOXC13. Similarly, knockdown of mixed lineage leukemia histone methylase (MLL)3 suppressed E2‐induced activation of HOXC13. MLLs (MLL1–MLL4) were bound to the HOXC13 promoter in an E2‐dependent manner. Knockdown of either ERα or ERβ affected the E2‐dependent binding of MLLs (MLL1–MLL4) into HOXC13 EREs, suggesting critical roles of ERs in recruiting MLLs in the HOXC13 promoter. Overall, our studies have demonstrated that HOXC13 is transcriptionally regulated by E2 and MLLs, which, in coordination with ERα and ERβ, play critical roles in this process. Although MLLs are known to regulate HOX genes, the roles of MLLs in hormone‐mediated regulation of HOX genes are unknown. Herein, we have demonstrated that MLLs are critical players in E2‐dependent regulation of the HOX gene.

Bisphenol-A induces expression of HOXC6, an estrogen-regulated homeobox-containing gene associated with breast cancer

“…In contrast to MLL2 and MLL3, the level of recruitment of MLL4 as well as the N-CoR was decreased upon treatment with either E2 or BPA, indicating potential involvment of MLL4 and N-CoR in the maintenace of basal transcription of HOXC6. This may indicate that there is an exchange of negative regulatory transcription factors with positive regulatory factors upon treatment with E2 or BPA, at the HOXC6 promoter and this type of exchange in transcription factors has been previously observed HOXC6 and other genes (14, 15, 41, 42, 44, 45, 48, 49, 73). Similar to E2, BPA exposure induced the epigenetic changes (histone modifications) at the HOXC6 promoter affecting its gene expression.…”

“…(60, 64, 65). Studies demonstrate that mixed lineage leukemia (MLL) family of histone methylases act as ER-coregulators during E2-mediated gene activation (14, 15, 44, 48, 49, 64–74). Herein, we examined, if ER and MLLs are involved in the E2 and BPA induced HOXC6 expression in MCF7 cells.…”

“…Notably, H3K4-trimethyl and histone acetylation are key to transcriptional activation. MLLs and CBP/p300 are well known H3K4-trimethylases and histone acetylases, respectively, that aid in gene activation (14, 15, 44, 48, 49, 51, 75). We treated MCF7 cells with E2 and BPA separately, fixed with formaldehyde and subjected to ChIP assay using antibodies against ERα, MLL1, MLL2, MLL3, MLL4, CBP, p300, N-CoR, H3K4-trimethyl, histone acetyl, RNAPII and β-actin (negative control).…”

“…There are several MLLs: MLL1, MLL2, MLL3, MLL4 and MLL5 (51, 71). Recent studies from our (and others) laboratory demonstrated that MLLs (MLL1–4) acts as ER-coregulators and associated with ER-mediated gene activation (14, 15, 45, 49, 63, 69). MLLs (MLL1–4) contains one or more LXXLL (nuclear receptor box or NR-box) domains through which they interact with nuclear receptors (NRs), get recruited to the NR-regulated gene promoters, introduces H3K4-trimethylation leading to gene activation (51, 71).…”

Bisphenol-A and diethylstilbestrol exposure induces the expression of breast cancer associated long noncoding RNA HOTAIR in vitro and in vivo

“…Cells were grown up to 60 % confluency in 60 mm culture plates and treated with varying concentrations of estradiol, BPA and DES for 4 h. Then the cells were harvested for RNA/protein extraction or for ChIP assays (Ansari et al 2009a; Ansari et al 2013a; Ansari et al 2013b; Bhan et al 2013). …”