Assessment of estrogen receptor--histone interactions.

Abstract

Several different in vitro binding assays show that the estrogen receptor from rabbit uterus interacts selectively with purified histones from calf thymus. The estrogen receptor binds strongly to histones H2B and H2A, moderately to histones H3 and H4, and poorly to histone HI. In the presence of histones H2B or H2A, the position at which the estrogen receptor focuses in an isoelectric gradient is shifted to a more basic zone. Kinetic experiments show that, if histone H2B is bound to a DNA, the estrogen receptor dissociates more slowly from that DNA. The portion of the estrogen receptor molecule required for binding to histone H2B is relatively stable to tryptic digestion; in contrast, the portion of the receptor molecule responsible for DNA binding is promptly lost during limited tryptic digestion. These in vitro findings suggest that the mechanism by which the estrogen receptor selectively alters gene expression may involve specific contacts with histone molecules.Steroid hormone receptors are regulatory proteins that can migrate from cytoplasm to nucleus and somehow alter the expression of specific genes (1-3). Although the precise nature of the interaction between steroid receptors and the genome remains unclear, many studies suggest that DNA and chromosomal proteins play an important role in the binding of the receptor complex to the nucleus (2-11). In particular, steroid hormone receptors can bind to isolated DNA in vitro (3-9). Yet, in vivo, virtually all the DNA in the eukaryotic nucleus is folded by histones into nucleosomes (1-14). Very little is known about how the receptor might recognize histone . Such recognition could occur in at least two general, nonexclusive ways. First, the receptor might recognize the presence (or absence) of critical histone molecules directly via a histone'receptor interaction. Alternatively, the receptor might not make direct contact with the histones, but the histones could induce changes in the secondary and tertiary structure of DNA and these changes could then serve as partial determinants of recognition. The limited interaction of steroids with histones (15, 16) could be attributed, at least in part, to trace amounts of steroid hormone receptors "contaminating" the histone fractions (17,18). Subsequent studies have shown that steroid hormone receptors can bind to histones and protamines in vitro (19)(20)(21)(22)(23), but these studies have often implied that the receptor-histone interactions were nonspecific.To explore the possibility ofdirect and specific receptor-histone interactions, we have used the estrogen receptor from rabbit uterus to address the following questions: (i) Does the estrogen receptor bind to histones? If so, do preferential interactions occur with certain histones? (ii) Do histones affect the physicochemical properties ofthe estrogen receptor? (iii) Do histones influence the binding of the estrogen receptor to DNA? (iv) Where on the estrogen receptor is the histone recognition site?

Expression profiling of estrogen responsive genes on bisphenol A, 4-nonylphenol and 17β-estradiol treatment using in house cDNA microarray

“…Among the genes regulated by the 3 estrogenic compounds, we have interested in Matrix Gla protein (MGP), H2A histone family, member X mRNA (H2AFX) and breast cancer 1, early onset (BRCA1). Although the up-regulation of these genes (MGP, H2AFX and BRCA1) by E2 treatment was previously reported [29][30][31] , it is first reported that these genes show the alteration of gene expression followed by not only E2 but alkylphenols (BPA and NP) treatment in this study. MGP is an important inhibitor of pathologic calcification, and deficiency contributes to pathogenesis of cardiovascular calcifications in dialysis patients.…”

“…This gene encodes a member of the histone H2A family, and generates two transcripts through the use of the conserved stem-loop termination motif, and the polyA addition motif. In vitro findings suggest that the mechanism by which the estrogen receptor selectively alters gene expression may involve specific contacts with histone molecules 30 . BRCA1, which functions as a tumor suppressor in human breast cancer cells, is a nuclear phosphoprotein which associates with RNA polymerase II holoenzyme.…”

Correlation between tyrosine hydroxylase activity, melanogenesis, and estradiol binding in human melanoma cells

“…It indicates the presence of characteristic estrogen-binding components or receptors, as monitored by their striking uptake and retention of tritiated hexosterol [35] or estradiol given in vivo or in vitro [36][37][38][39][40]. In particular, steroid hormone receptors can bind to isolated DNA in vitro [43][44][45][46][47][48][49] and interact selectively with purified histones from calf thymus [54]. DNA and chromosomal proteins play an important role in the binding of the receptor complex to the nucleus [42][43][44][45][46][47][48][49][50][51][52][53].…”

Estrogen‐Initiated Protein Interactomes During Embryo Implantation

“…It has a high affinity for another interacting partner of ERα during WOI, histones H2B and H2A, and a moderate affinity for histones H4 and H3, but only a weak to negligible affinity for histone H1. Thus, estrogen receptor has binding sites not only for estrogen and DNA but also for histones . The extent to which it binds to histones in the intact nucleus and the functional significance of this binding remain to be established.…”