We previously demonstrated that the estrogen response module (mERM) of the mouse lactoferrin gene, which contains an overlapping chicken ovalbumin upstream promoter transcription factor (COUP-TF)-and estrogen receptor-binding element, is responsible for estrogen induction. In this report we show that COUP-TF represses the mERM response to estrogen stimulation. Mutation and deletion of the COUP-TF-binding element or reduction of the endogenous COUP-TF increases mERM estrogen responsiveness. Likewise, overexpression of the COUP-TF expression vector blocked the estrogen-stimulated response of mERM in transfected cells. The molecular mechanism of this repression is due to the competition between COUP-TF and the estrogen receptor for binding at identical contact sites in the overlapping region of the mERM. Our results indicate that two members of the steroid-thyroid receptor superfamily work in concert to modulate lactoferrin gene expression.Regulation of gene expression at the transcriptional level is a complex process. The expression of a gene is controlled by multiple trans-acting factors that interact with each other and with the cluster of cis-acting DNA elements in regulated promoters (11,61). The estrogen receptor (ER), an estrogendependent transcription factor, mediates a variety of estrogenic effects on target tissues at the molecular level (2,11,17,24). Through gene transfers and deletion studies, the cis-acting DNA sequences that are responsible for estrogen regulation have been identified in various estrogen-regulated genes (3,7,23,46,52). ER, upon binding to the consensus palindromic estrogen response element (ERE), is able to confer estrogen-stimulated transcription. Recent studies show that the response elements for steroid hormones could also act together with other transcription factor-binding elements to bring about hormone-dependent responses (1,8,12,50,60). The trans activation of these genes is initiated by the interaction between ER and other transcription factors and their respective cognated elements.In addition to the steroid hormone receptors that responded to well-known ligands, a large collection of orphan receptors that share structural homology has been isolated, although the particular ligand has not yet been identified (28,51,57,58). One of those is the well-characterized chicken ovalbumin upstream promoter transcriptional factor (COUP-TF) (57, 58). COUP-TF was originally found through its interaction with a response element in the chicken ovalbumin gene promoter (48) and has been shown to play both positive and negative roles in gene regulation upon binding to various regulatory elements (5,6,20,25,32,37,54). These diverse roles highlight the importance of COUP-TF in the regulation of gene expression in various tissues. We previously found that the estrogen response module (mERM) of the mouse lactoferrin gene was composed of an overlapping ERE and COUP-TF-binding element (31,32).Band shift assay showed that both ER and COUP-TF specifically interacted with the mERM (32). Therefore, the...

Cisplatin resistance hinders the efficacy of chemotherapy in ovarian cancer. MicroRNAs (miRs) have been implicated in drug resistance in anti-cancer chemotherapy. We compared the expression profiles of miRs between cisplatin-resistant and cisplatin-sensitive ovarian cancer cells, and found that miR-216b was significantly downregulated in cisplatin-resistant ovarian cancer cells. To investigate its molecular mechanism, we performed cell viability and apoptosis assays in cisplatin-resistant ovarian cells, and found that miR-216b reduced cell viability and promoted apoptosis. Although 4 potential targets were obtained through bioinformatics, only the mRNA level of poly(ADP-ribose) polymerase (PARP)-1 was significantly regulated by miR-216b. Disruption of the complementary binding sequence of miR-216b on the 3'-untranslated region (3'-UTR) of the PARP1 led to the loss of miR-216b targeting. Spearman's correlation coefficient of the levels of miR-216b and PARP1 mRNA from 51 human ovarian cancer specimens also showed a significantly negative correlation between them. Importantly, the improved cisplatin sensitivity induced by miR-216b was markedly reversed by PARP1 overexpression. Tumor formation assay in nude mice further provided an evidence on the suppressive role of miR-216b in tumor growth. Taken together, this study demonstrated that a new miRNA, miR-216b, was involved in cisplatin resistance in ovarian cancer, which could be regarded as a potential sensitizer in cisplatin chemotherapy.

Two recent genome-wide association studies of East Asian populations revealed three genetic variants in WDFY4/LRRC18 associated with systemic lupus erythematosus (SLE). To identify the gene contributing to this disease susceptibility, we examined the mRNA expression of WDFY4 and LRRC18 in patients with SLE and healthy controls. WDFY4 was significantly downregulated in SLE patients as compared with controls. We used allelic expression and dual-luciferase assays to identify the functional variant. Transcriptional activity was lower for the rs877819A than -G allele. Electrophoretic mobility shift and supershift assays revealed that the transcription factor Yinyang1 (YY1) binds to rs877819, with lower affinity to the A allele, which explained the reduced transcriptional activity. This effect was further confirmed by YY1 small interfering RNA knockdown, overexpression and chromatin immunoprecipitation experiments. rs877819 in WDFY4 might be the functional site associated with SLE by reduced binding of YY1 and downregulating WDFY4 expression.