Transcriptional activation of the human hematopoietic prostaglandin D synthase gene in megakaryoblastic cells. Roles of the oct-1 element in the 5'-flanking region and the AP-2 element in the untranslated exon 1

The human hematopoietic prostaglandin D synthase (H-PGDS) gene is highly expressed in human megakaryoblastic cells, in which phorbol ester induces its expression. We characterized the promoter activity of the 5'-flanking region and the untranslated exon 1 (-1044 to +290) of the human H-PGDS gene in human megakaryoblastic Dami cells. Transient expression analysis using the luciferase reporter gene revealed that the 5'-flanking region and the untranslated exon 1 were sufficient for efficient expression of the H-PGDS gene in Dami cells, but not in monocytic U937 cells. Deletion and site-directed mutagenesis of the Oct-1 element in the 5'-flanking region decreased the promoter activity by approximately 30% compared with that of the entire region from -1044 to +290. An electrophoretic mobility shift assay demonstrated that Oct-1 specifically bound to the promoter region. Interestingly, even only untranslated exon 1 (+1 to +290) showed approximately 60% of the promoter activity of the entire region from -1044 to +290. Site-directed mutagenesis of the AP-2 element within the untranslated exon 1 abolished the basal promoter activity as well as its phorbol ester-mediated up-regulation. In AP-2-deficient HepG2 cells, the H-PGDS promoter activity was enhanced by coexpression with AP-2alpha. These findings indicate that the Oct-1 element in the 5'-flanking region acts as a positive cis-acting element and that the AP-2 element in the untranslated exon 1 is crucial for both basal and phorbol ester-mediated up-regulation of human H-PGDS gene expression in megakaryoblastic Dami cells.     

Structure and sequence analysis of the human activin beta A subunit gene.

The cloned genomic DNA containing the human activin beta A subunit gene were analyzed by restriction endonuclease mapping, Southern blotting and DNA sequencing. The activin gene is composed of two exons interrupted by the 9-kb intron. The TATA, CCAAT and CT-stretch sequences were found in the 5'-flanking region of the gene. An intronic sequence contained SV40 enhancer core element in the vicinity of the exon 1. In the 3'-flanking region, we identified eight consensus polyadenylation sequences, five ATTTA motifs, CA element consisting of (CA)14, AP-1 binding site and two SV40 enhancer core elements. A dot matrix analysis revealed the high degree of conservation between the human and rat sequences within the 3'-flanking region, suggesting a possible functional significance.     

Structure of the human laminin B2 chain gene reveals extensive divergence from the laminin B1 chain gene

The exon-intron structure of the human laminin B2 chain gene was elucidated from genomic lambda phage clones spanning 2 kilobase pairs (kb) of the 5'-flanking region, 58 kb of the structural gene and 10 kb of the 3'-flanking region. The entire gene was shown to contain 28 exons. The promoter region has no TATA or CAAT boxes whereas it contains five GC boxes and three AP-2-like binding sites. Comparison with the promoter region of the mouse gene revealed six highly conserved sequences of 14 to 42 base pairs in length. Sequencing of the last exon of the gene showed that the 3'-untranslated region of the mRNA can be up to 2797 nucleotides with five AATAAA potential polyadenylation signals. The similarity of the human 3'-untranslated sequence with that of mouse was shown to be 68.8%. The exon-intron structure of the laminin B2 chain gene demonstrated extensive divergence from the human laminin B1 chain gene, which has 34 exons. Only three intron locations are conserved in these two genes. The overall exon profile of the laminin B2 chain gene correlates only marginally with the pattern of structural domains and internal cysteine-rich repeats in the laminin B2 polypeptide chain.     

A role for CBS domain 2 in trafficking of chloride channel CLC-5

CLC-5 is a member of the CLC family of voltage-gated chloride channels. Mutations disrupting CLC-5 lead to Dent's disease, an X-linked renal tubular disorder, characterised by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis, and renal stones. Sequence analysis of CLC-5 reveals a 746 amino acid protein with an intracellular amino-terminus, transmembrane spanning domains, and two CBS domains within its intracellular carboxy-terminus. CBS domains have been implicated in intracellular targetting and trafficking as well as protein-protein interactions. We investigate subcellular localisation of three naturally occurring CLC-5 mutants which all lead to a truncated protein, disrupting the second CBS domain. These mutants are unable to traffic normally to acidic endosomes but are retained in perinuclear compartments, colocalising with the Golgi complex. This is the first identification of the cellular pathogenesis of CBS domain mutations of CLC-5.     

Identification and characterization of a novel repressor site in the human tumor necrosis factor alpha gene.

In human monocytic cell lines, tumor necrosis factor alpha (TNF alpha) expression is induced by phorbol myristate acetate (PMA). We have identified positive and negative cis-acting elements in the TNF alpha promoter by deletion analysis. Here we present the initial characterization of the repressor element. The repressor element was shown to function in either orientation and at various distances upstream from the positive element of the TNF alpha promoter. The TNF alpha repressor site (TRS) has been localized to a 25 bp region between base pairs -254 and -230 in the promoter. This region contains a 10 bp sequence with homology to the binding site of the activator protein AP-2. Mutation of the 6 C's of this 10 bp AP-2-like site abolish TRS repressor function. However, this AP-2-like site is not a binding site for AP-2 protein based on gel retardation analysis. In addition, a well-characterized AP-2-binding site placed upstream of the positive element of the TNF alpha gene did not cause repression. Therefore, this repression is very likely mediated by a novel protein(s) which interacts with the AP-2 consensus site in the TRS.