Potential Role of a Novel Transcriptional Coactivator PELP1 in Histone H1 Displacement in Cancer Cells

Abstract

The estrogen receptor plays an important role in breast cancer progression. Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1), also called modulator of nongenomic activity of estrogen receptor (MNAR), a novel coactivator of estrogen receptor, modulates estrogen receptor transactivation functions. The mechanisms by which PELP1 modulates estrogen receptor genomic functions is not known. Here, using biochemical and scanning confocal microscopic analysis, we have demonstrated nuclear localization and functional implications of PELP1. Subnuclear fractionation showed PELP1 association with chromatin and nuclear matrix fractions. Ligand stimulation promoted recruitment of PELP1 to 17␤-estradiol responsive promoters, its colocalization with acetylated H3, and increased PELP1-associated histone acetyltransferase enzymatic activity. Far Western analysis revealed that PELP1 interacts with histone 1 and 3, with more preference toward histone 1. Using deletion analysis, we have identified the PELP1 COOH-terminal region as the histone 1 binding site. The PELP1 mutant lacking histone 1-binding domain acts as a dominantnegative and blocks estrogen receptor ␣-mediated transcription. Chromatin immunoprecipitation analysis showed a cyclic association and dissociation of PELP1 with the promoter, with recruitment of histone 1 and PELP1 occurring in opposite phases. PELP1 overexpression increased the micrococcal nuclease sensitivity of estrogen response element-containing nucleosomes. Our results provide novel insights about the transcription regulation of PELP1 and suggest that PELP1 participates in chromatin remodeling activity via displacement of histone 1 in cancer cells.

Growth Factor Regulation of Estrogen Receptor Coregulator PELP1 Functions via Protein Kinase A Pathway

“…One of the notable findings of this study is the recruitment of PELP1 to discrete subnuclear foci after stimulation of the PKA signaling pathway. In our earlier study using subnuclear fractionation, we showed that substantial amount of PELP1 associated with the chromatin and nuclear matrix fractions (21). In this study, inhibition of PKA signaling substantially reduced the amount of PELP1 in the nuclear matrix fractions.…”

“…The wild-type PELP1, GST-PELP1, and ERE reporter constructs were described previously (21). The PELP1 S102A, S245A, S316A, S350A, S415A, S515A, S530A, and S613A mutations were generated by site-directed mutagenesis (Quick Change Mutagenesis kit, Stratagene) using GST-PELP1-1-400, GST-PELP1-400-600, GST-PELP1-600-880, and pcDNA-PELP1 as backbones.…”

“…The lysate was diluted to a salt concentration of 100 mmol/L before adding PELP1 antibodycoupled protein A beads. For cell fractionation, MCF-7 cells were serum starved for at least 24 h and treated with forskolin or H89 and fractionated into cytoplasmic, nucleoplasmic, chromatin, and nuclear matrix fractions as described (21). Equal amounts of protein were analyzed for localization of PELP1 by Western blotting.…”

“…PELP1 is a unique coactivator that plays an important role in both the genomic and nongenomic actions of the ER (20). PELP1 recruits to the ER target gene promoter, interacts with histones and histone-modifying enzymes, and is suggested to play a role in chromatin remodeling activity of the ligandbound ER (21). The ability of PELP1 to interact and couple cytosolic kinases c-Src and phosphatidylinositol-3-kinase to the ER highlights a novel role for PELP1 in nongenomic ER signaling (19,22,23).…”

The prognostic significance of PELP1 expression in invasive breast cancer with emphasis on the ER-positive luminal-like subtype

“…PELP1 maintains the balanced hypoacetylated state of histones, while ER binding reverses its role through hyperacetylation of histones through an unknown mechanism [5]. In addition, it has been suggested that PELP1 contributes to chromatin remodelling by affecting certain types of histone in cancer cells [6]. In a previous, breast cancer study, PELP1 expression was reported to be up-regulated in higher grade lymph nodepositive invasive tumours [7], but the study did not specifically focus on PELP1 expression in ER?/luminal cancers.…”