Cloning and Transcriptional Activity Analysis of the Porcine Abcb1 Gene Promoter: Transcription Factor Sp1 Regulates the Expression of Porcine Abcb1

Transcriptional Regulation of the Chicken ASMT Gene- A Preliminary Analysis

1. Melatonin is an indole hormone that, among its myriad biological functions, regulates circadian and seasonal rhythms in animals. The ASMT gene plays an essential role in melatonin synthesis. However, in chickens, little is known about the regulatory elements governing its transcription.2. The following study identified the transcription start site of the chicken ASMT gene by 5'-RACE. Then, the proximal minimal promoter was identified using a series of 5' truncations of the ASMT promoter (e.g., -3502/+17, -2698/+17, -2003/+17, -1378/+17, and -254/+17). Site-directed mutagenesis, overexpression, and electrophoretic mobility shift assay (EMSA) were applied to show that the transcription factor Oct-1 binds to the promoter region of ASMT.3. The translation start site was located 19 bp upstream from the translational start site. The luciferase reporter assay confirmed that the core promoter of chicken ASMT gene was in the -254/+17 region. Using site-directed mutagenesis, overexpression, and EMSA, Oct-1 bound the promoter of ASMT.4. Overall, Oct1 plays an important role in the transcriptional regulation of chicken ASMT gene.

P-glycoprotein: new insights into structure, physiological function, regulation and alterations in disease

The multidrug resistance phenomenon presents a major threat to the pharmaceutical industry. This resistance is a common occurrence in several diseases and is mediated by multidrug transporters that actively pump substances out of the cell and away from their target regions. The most well-known multidrug transporter is the P-glycoprotein transporter. The binding sites within P-glycoprotein can accommodate a variety of compounds with diverse structures. Hence, numerous drugs are P-glycoprotein substrates, with new ones being identified every day. For many years, the mechanisms of action of P-glycoprotein have been shrouded in mystery, and scientists have only recently been able to elucidate certain structural and functional aspects of this protein. Although P-glycoprotein is highly implicated in multidrug resistant diseases, this transporter also performs various physiological roles in the human body and is expressed in several tissues, including the brain, kidneys, liver, gastrointestinal tract, testis, and placenta. The expression levels of P-glycoprotein are regulated by different enzymes, inflammatory mediators and transcription factors; alterations in which can result in the generation of a disease phenotype. This review details the discovery, the recently proposed structure and the regulatory functions of P-glycoprotein, as well as the crucial role it plays in health and disease.

Pharmacodynamic mechanisms of anti-inflammatory drugs on the chemosensitization of multidrug-resistant cancers and the pharmacogenetics effectiveness

Drug resistance as a remarkable issue in cancer treatment is associated with inflammation which occurs through complex chemical reactions in the tumor microenvironment. Recent studies have implicated that glucocorticoids and NSAIDs are mainly useful combinations for inflammatory response modulation in chemotherapeutic protocols for cancer treatment. Immunosuppressive actions of glucocorticoids and NSAIDs are mainly mediated by the transrepression or activation regulation of inflammatory genes with different DNA-bound transcription factors including AP-1, NFAT, NF-κB, STAT and also, varying functions of COX enzymes in cancer cells. Interestingly, many investigations have proved the benefits of these anti-inflammatory agents in the quenching of multidrug resistance pathways. Numerous analyses on the ABC transporter promoters showed conserved nucleotide sequences with several DNA response elements that participate in transcriptional regulation. Furthermore, genetic variations in nucleotide sequences of membrane transporters were strongly associated with changes in these transporters' expression or function and a substantial impact on systemic drug exposure and toxicity. It appeared that several polymorphisms in MDR transporter genes especially MDR1 have influenced the regulatory mechanisms and explained differences in glucocorticoid responses.

Identification of Functional Transcriptional Binding Sites within Chicken Abcg2 Gene Promoter and Screening Its Regulators

Breast cancer resistance protein (BCRP), an ATP-binding cassette (ABC) half transporter encoded by the Abcg2 gene, is reported to influence the pharmacokinetics of substrate drugs during clinical therapy. The aim of this study was to clarify the mechanisms that regulate the transcription of the chicken Abcg2 gene through cloning and characterization of its promoter region. Results showed that the Abcg2 gene is transcribed by a TATA-less promoter with several putative Sp1 sites upstream from two putative CpG islands. A luciferase reporter assay conducted both in chicken leghorn male hepatoma (LMH) cells and chicken primary hepatocytes mapped a basal promoter to nucleotides -110 to +30, which is responsible for the constitutive expression of Abcg2. The 5'-region upstream of the basal promoter was characterized by both positive and negative regulatory domains. Further, using the cell-based reporter gene assay combined with RT-PCR and drug accumulation analysis, we found that four xenobiotics, daidzein, clotrimazole, ivermectin, and lipopolysaccharide (LPS), influence the expression and function of BCRP through significant regulation of the Abcg2 gene promoter. Interaction sites with the Abcg2 gene promoter of these four selected regulators were clarified by progressive deletions and mutation assays. This study shed some light on the regulatory mechanisms involved in chicken Abcg2 gene expression and the results may have far-reaching significance regarding the usage and development of veterinary drugs.