c BHLHE40 and BHLHE41 (BHLHE40/41) are basic helix-loop-helix type transcription factors that play key roles in multiple cell behaviors. BHLHE40/41 were recently shown to be involved in an epithelial-to-mesenchymal transition (EMT). However, the precise mechanism of EMT control by BHLHE40/41 remains unclear. In the present study, we demonstrated that BHLHE40/41 expression was controlled in a pathological stage-dependent manner in human endometrial cancer (HEC). Our in vitro assays showed that BHLHE40/41 suppressed tumor cell invasion. BHLHE40/41 also suppressed the transcription of the EMT effectors SNAI1, SNAI2, and TWIST1. We identified the critical promoter regions of TWIST1 for its basal transcriptional activity. We elucidated that the transcription factor SP1 was involved in the basal transcriptional activity of TWIST1 and that BHLHE40/41 competed with SP1 for DNA binding to regulate gene transcription. This study is the first to report the detailed functions of BHLHE40 and BHLHE41 in the suppression of EMT effectors in vitro. Our results suggest that BHLHE40/41 suppress tumor cell invasion by inhibiting EMT in tumor cells. We propose that BHLHE40/41 are promising markers to predict the aggressiveness of each HEC case and that molecular targeting strategies involving BHLHE40/41 and SP1 may effectively regulate HEC progression. Basic helix-loop-helix (bHLH) type transcription factors play key roles in cell differentiation, proliferation, apoptosis, and metabolism. BHLHE40 (basic helix-loop-helix family member e40 gene) and BHLHE41 are members of the Hairy/E(spl)/HES family. BHLHE40 and BHLHE41 (BHLHE40/41) exhibit more than 90% similarity in the bHLH region and approximately 50% in total. BHLHE40/41 have been shown to function as transcriptional repressors by binding to the class B E-box. BHLHE40/41 interact with TF2B, TBP, or TF2D or recruit a histone deacetylase at the E-box site (1-5). On the other hand, BHLHE40/41 were previously reported to modulate the expression of some genes in an E-box-independent manner. BHLHE40 has been shown to associate with SP1 binding sites in the BIRC5 promoter to activate its transcription (6) and with STAT3 to regulate the transcription of STAT3-dependent target genes (7). BHLHE41 suppressed VEGF transcription by interacting with HIF1A (8). BHLHE40 and BHLHE41 were reported to associate with retinoid X receptor (RXR), MYOD1, or CEBP in order to regulate the transcription of their target genes (9-12).In diverse types of cancer species, such as colon, oral, and liver cancer or brain tumors, BHLHE40 expression levels were found to be higher in tumors than in adjacent normal tissues (13-15). On the other hand, in human endometrial cancer (HEC) and nonsmall-cell lung cancer, no changes in BHLHE40 expression were reported between cancer and normal tissues (16,17). Regarding expression profiles with the development of cancer, studies on oral, lung, liver, and esophageal cancer showed that BHLHE40 expression inversely correlated with the tumor stage or differentiation grade (18-21)...

SummarySpectral characterization of 5, 6-epoxyretinal isomers (II) prepared by a regioselective epoxidation of the parent retinal isomers have been described. High-performance liquid chromatographic separation of epoxyretinals and a photoisomerization behavior of all-trans-5 , 6 epoxyretinal (IIa) have been investigated. Key Words 5, 6-epoxyretinal, regioselective epoxidation, high-perfor mance liquid chromatography, photoisomerization , spectral analysis, retinal Bovine rhodopsin has been shown to contain 11-cis-retinal (Ic) bound via a Schif-base linkage (1, 2), to the c-amino group of a specific lysyl residue (3) of the apoprotein, opsin. However, the interaction of each part of 11-cis-retinal (Ic) with opsin in the rhodopsin molecule and the chromophoric structures of the unstable intermediate during the photobleaching process of rhodopsin have not been clarified chemically in detail. On the other hand, 5, 6-epoxyretinoic acid has recently been noted with regard to the metabolism of retinol (vitamin A alcohol) and retinoic acid (vitamin A acid) (4, 5). In a previous communication (6), we reported on 5, 6 epoxyrhodopsin as a part of the studies to elucidate the protein-chromophore interaction in rhodopsin. In this paper, we describe the spectral characterization of 5, 6-epoxyretinal isomers (ha-lid), their separation by high-performance liquid chromatography (HPLC), and the photoisomerization behavior of all-trans-5, 6 epoxyretinal (ha). MATERIALS AND METHODSUltraviolet (UV) spectra were recorded on a Shimadzu UV 2005 instrument .

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