Immunohistochemical analysis of secretoglobin SCGB 2A1 expression in human ocular glands and tissues

Human secretoglobin (SCGB) 2A1 (or lipophilin C, lacryglobin, mammaglobin B) is a small protein of unknown function that forms heterodimers with secretoglobin 1D1 (lipophilin A) in tears. SCGB 2A1 is homologous to mammaglobin (mammaglobin A) and the C3 component of prostatein, the major secretory protein of the rat ventral prostate. Androgen-dependent expression of SCGB 2A1 has been observed in the prostate. Besides identification of SCGB 2A1 in the tear proteome only its mRNA had been detected in the lacrimal gland. Here, we report expression of SCGB 2A1 in all ocular glands and in the keratinized stratified squamous epithelium of the eyelid as well as in the stratified epithelium of the conjunctiva and in the orbicularis oculi muscle. Almost all of these tissues are also known to express the androgen receptor. Therefore, we conclude that presence of the androgen signalling machinery could be the main general determinant of SCGB 2A1 expression. Implications of the presence in tear fluid of an androgen-regulated secretoglobin, which most likely binds hydrophobic ligands, for tear film lipid layer formation and function is discussed.     

Suppression of the androgen receptor function by quercetin through protein–protein interactions of Sp1, c-Jun, and the androgen receptor in human prostate cancer cells

We have previously reported that the increase in c-Jun expression induced by quercetin inhibited androgen receptor (AR) transactivation, and Sp1 was involved in quercetin-mediated downregulation of AR activity. Transient transfection assays in this work revealed that co-expression of c-Jun quenched Sp1-induced production of luciferase activity driven by AR promoter or three copies of Sp1 binding elements in the AR promoter. Moreover, c-Jun repressed AR-mediated luciferase activity via androgen-response elements (AREs) of the hK2 gene, while this suppression could be restored partially by cotransfection of Sp1 expression plasmid. The physical associations of c-Jun, Sp1, and AR induced by quercetin were further demonstrated by co-immunoprecipitation experiments. In addition, quercetin-mediated repression of AR expression and activity was partially reversed by blocking of JNK signaling pathway. These results suggested that c-Jun might play an important role in the suppression of AR expression and activity in the presence of quercetin, and association of a c-Jun/Sp1/AR protein complex induced by quercetin represented a novel mechanism that was involved in down-regulation of the AR function in prostate cancer cells.     

Regulation of human microsomal prostaglandin E synthase-1 by IL-1β requires a distal enhancer element with a unique role for C/EBPβ

The studies of PGE2 (prostaglandin E2) biosynthesis have focused primarily on the role of cyclo-oxygenases. Efforts have shifted towards the specific PGE2 terminal synthases, particularly mPGES-1 (microsomal PGE synthase 1), which has emerged as the crucial inducible synthase with roles in pain, cancer and inflammation. mPGES-1 is induced by pro-inflammatory cytokines with studies focusing on the proximal promoter, mediated specifically through Egr-1 (early growth-response factor 1). Numerous studies demonstrate that the mPGES-1 promoter (PTGES) alone cannot account for the level of IL-1β (interleukin 1β) induction. We identified two DNase I-hypersensitive sites within the proximal promoter near the Egr-1 element and a novel distal site near -8.6 kb. Functional analysis of the distal site revealed two elements that co-operate with basal promoter expression and a stimulus-dependent enhancer. A specific binding site for C/EBPβ (CCAAT/enhancer-binding protein β) in the enhancer was directly responsible for inducible enhancer activity. ChIP (chromatin immunoprecipitation) analysis demonstrated constitutive Egr-1 binding to the promoter and induced RNA polymerase II and C/EBPβ binding to the promoter and enhancer respectively. Knockout/knockdown studies established a functional role for C/EBPβ in mPGES-1 gene regulation and the documented interaction between Egr-1 and C/EBPβ highlights the proximal promoter co-operation with a novel distal enhancer element in regulating inducible mPGES-1 expression.     

Sp1 binding sites and an estrogen response element half-site are involved in regulation of the human progesterone receptor A promoter

Progesterone receptor gene expression is induced by estrogen in MCF-7 human breast cancer cells. Although it is generally thought that estrogen responsiveness is mediated through estrogen response elements (EREs), the progesterone receptor gene lacks an identifiable ERE. The progesterone receptor A promoter does, however, contain a half-ERE/Sp1 binding site comprised of an ERE half-site upstream of two Sp1 binding sites. We have used in vivo deoxyribonuclease I (DNase I) footprinting to demonstrate that the half-ERE/Sp1 binding site is more protected when MCF-7 cells are treated with estrogen than when cells are not exposed to hormone, suggesting that this region is involved in estrogen-regulated gene expression. The ability of the half-ERE/Sp1 binding site to confer estrogen responsiveness to a simple heterologous promoter was confirmed in transient cotransfection assays. In vitro DNase I footprinting and gel mobility shift assays demonstrated that Sp1 present in MCF-7 nuclear extracts and purified Sp1 protein bound to the two Sp1 sites and that the estrogen receptor enhanced Sp1 binding. In addition to its effects on Sp1 binding, the estrogen receptor also bound directly to the ERE half-site. Taken together, these findings suggest that the estrogen receptor and Sp1 play a role in activation of the human progesterone receptor A promoter.