Ligand-Controlled Interaction of Histone Acetyltransferase Binding to ORC-1 (HBO1) with the N-Terminal Transactivating Domain of Progesterone Receptor Induces Steroid Receptor Coactivator 1-Dependent Coactivation of Transcription

Abstract

Modulators of cofactor recruitment by nuclear receptors are expected to play an important role in the coordination of hormone-induced transactivation processes. To identify such factors interacting with the N-terminal domain (NTD) of the progesterone receptor (PR), we used this domain as bait in the yeast Sos-Ras two-hybrid system. cDNAs encoding the C-terminal MYST (MOZ-Ybf2/Sas3-Sas2-Tip60 acetyltransferases) domain of HBO1 [histone acetyltransferase binding to the origin recognition complex (ORC) 1 subunit], a member of the MYST acetylase family, were thus selected from a human testis cDNA library. In transiently transfected CV1 cells, the wild-type HBO1 [611 amino acids (aa)] enhanced transcription mediated by steroid receptors, notably PR, mineralocorticoid receptor, and glucocorticoid receptor, and strongly induced PR and estrogen receptor coactivation by steroid receptor coactivator 1a (SRC-1a). As assessed by two-hybrid and glutathione-S-transferase pull-down assays, the HBO1 MYST acetylase domain (aa 340-611) interacts mainly with the NTD, and also contacts the DNA-binding domain and the hinge domains of hormone-bound PR. The HBO1 N-terminal region (aa 1-340) associates additionally with PR ligand-binding domain (LBD). HBO1 was found also to interact through its NTD with SRC-1a in the absence of steroid receptor. The latter coassociation enhanced specifically activation function 2 activation function encompassed in the LBD. Conversely, the MYST acetylase domain specifically enhanced SRC-1 coupling with PR NTD, through a hormone-dependent mechanism. In human embryonic kidney 293 cells expressing human PRA or PRB, HBO1 raised selectively an SRC-1-dependent response of PRB but failed to regulate PRA activity. We show that HBO1 acts through modification of an LBD-controlled structure present in the N terminus of PRB leading to the modulation of SRC-1 functional coupling with activation function 3-mediated transcription. Importantly, real-time RT-PCR analysis also revealed that HBO1 enhanced SRC-1 coactivation of PR-dependent transcription of human endogenous genes such as alpha-6 integrin and 11beta-hydroxydehydrogenase 2 but not that of amphiregulin. Immunofluorescence and confocal microscopy of human embryonic kidney-PRB cells demonstrated that the hormone induces the colocalization of HBO1 with PR-SRC-1 complex into nuclear speckles characteristic of PR-mediated chromatin remodeling. Our results suggest that HBO1 might play an important physiological role in human PR signaling.

Genetic Alterations and Oncogenic Pathways Associated with Breast Cancer Subtypes

“…MYST2, the only gene in the amplicon on 17q21 to meet all three selection criteria, encodes the HBO1 histone acetyltransferase implicated in the regulation of DNA synthesis (31,34,59,60). HBO1 has also been shown to enhance transcription mediated by steroid receptors including ER and PR (32,33,61). Our finding that overexpression of MYST2 enhances colony formation in soft agar by SKBR3 cells, which are HER2 + , suggests that MYST2 is a bona fide oncogene that acts independently of ER and PR.…”

“…In the amplicon around 45 Mbp on chromosome 17q21 (Fig. 4B), which is associated with the ER + /PR + and HER2 + subtypes, there is a single gene that fulfills all three criteria: MYST2, which encodes a histone acetyltransferase (HBO1) that has been implicated in the regulation of DNA synthesis and in steroid hormone receptor signaling (31)(32)(33)(34). In the amplicon around 55 Mbp (17q23), PPM1D is the only gene meeting all three criteria, although it is not strongly supported by any individual line of evidence.…”

The MYST family of histone acetyltransferases and their intimate links to cancer

“…HBO1 has been variously reported to function as a repressor of transcription by the AR (Sharma et al, 2000) and NF-kB (Contzler et al, 2006), or as a co-activator for a number of other nuclear hormone receptors (Georgiakaki et al, 2006). Similarly, contradictory roles in transcription have also been attributed to the Drosophila orthologue of HBO1 (Grienenberger et al, 2002;Miotto et al, 2006).…”

Differential modulation of glucocorticoid and progesterone receptor transactivation

“…Many factors equally affect the maximal levels of PR-and GR-mediated gene expression, or V max (McKenna et al, 1999;Giannoukos et al, 2001;Hosohata et al, 2003;Webster et al, 2003;Kino et al, 2004;Zhang et al, 2004;Dong et al, 2005). However, factors that preferentially alter the transactivation of PR vs. GR are being increasingly described (Tan et al, 2000;Fernandes et al, 2003;Metzger et al, 2003;Dhananjayan et al, 2006;Georgiakaki et al, 2006;Sanchez et al, 2007;Zhao et al, 2007). PR is reported to selectively recruit the coactivator SRC-1 and the comodulator CBP to acetylate K5 on histone H4 while GR preferentially recruits TIF2 and then PCAF to histone H3 to cause phosphorylation (S10) and acetylation (K14) and demethylation (K9) .…”