Transcription of the promoter of the rat NF-1 gene depends on the integrity of an Sp1 recognition site

Ethanol feeding alters death signaling in the pancreas

OBJECTIVES

Alcohol abuse is a major cause of pancreatitis, which is associated with death of parenchymal cells. The goal of this study was to explore the effects of ethanol on cell death pathways in the pancreas.

METHODS

Adult male Wistar rats were fed with ethanol diets using the Lieber-DeCarli method. Caspase-8, caspase-3, and cathepsin B expression and activity in the pancreas of these animals as well as the signals that regulate their expression were studied using Western blot analysis and specific assays for biochemical enzyme activity.

RESULTS

In the pancreas from rats fed with ethanol, the protein expression and activity of caspase-8 decreased by 48% and 45%, respectively, and caspase-3 activity decreased by 39%. In contrast, cathepsin B protein expression and activity increased with ethanol feeding by 189% and 143%, respectively. Evaluation of the transcriptional regulatory system for caspase-8 and cathepsin B showed that the ethanol effects on these pathways were largely transcriptional.

CONCLUSIONS

Our findings show effects of ethanol on the expression of several signals involved in cell death in the pancreas through alteration of transcriptional regulators. The decrease in caspase expression and increase in cathepsin B expression indicate that ethanol feeding may prevent apoptosis and promote necrosis of pancreatic tissue with stresses that cause pancreatitis.

Mouse BTEB3, a new member of the basic transcription element binding protein (BTEB) family, activates expression from GC-rich minimal promoter regions

Members of the three-zinc-finger family of transcription factors play an important role in determining basal transcription. We have cloned mouse BTEB3 (mBTEB3), a new member of the basic transcription element binding protein (BTEB) family, which is expressed in a wide variety of tissues. mBTEB3 activates transcription of the simian virus 40 early promoter (4-fold) and of the tissue-specific SM22alpha promoter (100-fold), suggesting that, like BTEB1 and Sp1, mBTEB3 is a basal transcription factor.

Point mutations within 663-666 bp of intron 6 of the human TDO2 gene, associated with a number of psychiatric disorders, damage the YY-1 transcription factor binding site

Single base mutations G-->A at position 663 and G-->T at position 666 of intron 6 of the human tryptophan oxygenase gene (TDO2) are associated with a variety of psychiatric disorders [Comings, D.E. et al. (1996) Pharmacogenetics 6, 307-318]. Binding of rat liver nuclear extract proteins to synthetic double-strand oligonucleotides corresponding to three allelic states of the region between 651 bp and 680 bp of human TDO2 intron 6 has been studied by gel shift assay. It has been demonstrated that to each allelic state of the region there corresponds a specific set of proteins that interacts with it. With the aid of computer analysis and using specific anti-YY-1 antibodies it has been shown that both mutations damage the YY-1 transcription factor binding site.

Identification of NFI-binding sites and cloning of NFI-cDNAs suggest a regulatory role for NFI transcription factors in olfactory neuron gene expression

Olfactory receptor neurons are responsible for the detection and signal transduction of odor ligands. Several genes associated with this activity are preferentially or exclusively expressed in these neurons. Among these genes are those coding for olfactory receptors, adenylyl cyclase type III, the cyclic nucleotide gated olfactory channel 1 (OcNC-1), Galpha(olf) and the olfactory marker protein (OMP). Promoter analyses of these genes identified a binding site for the new transcription factor family O/E whose initial member, Olf-1, is abundantly expressed in olfactory neurons. We report here that the proximal promoters of three of these genes, that are selectively expressed in olfactory neurons, each contains a functional NFI binding site and that the sites have different affinities for NFI proteins indicating a regulatory role for NFI proteins in olfactory gene expression. We further demonstrate, by cloning, that all four NFI genes are expressed in the olfactory nasal mucosa. Analysis by in situ hybridization illustrates that at least three of these gene products are expressed in the neuroepithelium in which the olfactory neurons reside. NFI proteins are capable of functioning as positive or negative regulators of transcription depending on the tissue, cell-type, age, and gene in question. These multivalent functions of NFI could be achieved by temporally and spatially regulated expression of distinct subsets of NFI isoforms. It now remains to characterize the tissue and cell specific patterns of expression of distinct NFI transcription factors during ontogeny and their roles in regulating gene expression.

Regulation of expression within a gene family. The case of the rat gammaB- and gammaD-crystallin promoters

The six closely related and clustered rat gamma-crystallin genes, the gammaA- to gammaF-crystallin genes, are simultaneously activated in the embryonic lens but differentially shut down during postnatal development with the gammaB-crystallin gene, the last one to be active. We show here that developmental silencing of the gammaD-crystallin promoter correlates with delayed demethylation during lens fiber cell differentiation. Methylation silencing of the gammaD-crystallin promoter is a general effect and does not require the methylation of a specific CpG, nor does methylation interfere with factor binding to the proximal activator. In later development, the gammaD-crystallin promoter is also shut down earlier by a repressor that footprints to the -91/-78 region. A factor with identical properties is present in brain. Hence, a ubiquitous factor has been recruited as a developmental regulator by the lens. All gamma-crystallin promoters tested contain upstream silencers, but at least the gammaB-crystallin silencer is distinct from the gammaD-crystallin silencer. The gamma-crystallin promoters were found to share a proximal activator (the gamma-box; around -50), which behaves as a MARE. The gammaB-box is recognized with much lower avidity than the gammaD-box. By swapping elements between the gammaB- and the gammaD-crystallin promoter, we show that activation by the gammaB-box requires a directly adjacent -46/-38 AP-1 consensus site. These experiments also uncovered another positive element in the gammaD-crystallin promoter, around -10. In the context of the gammaD-crystallin promoter, this element is redundant; in the context of the gammaB-crystallin promoter, it can replace the -46/-38 element.

A bidirectional promoter connects the p14.5 gene to the gene for RNase P and RNase MRP protein subunit hPOP1

We have identified the functional promoter of the translational inhibitor p14.5, the human homologue to a rat perchloric acid-soluble protein (PSP), a mouse heat-responsive protein (Hrp12) and a goat tumor antigen (UK114). Sequence analysis revealed a GC-rich promoter with several consensus sequences for transcription factors, but no TATA- and CAAT-box. To confirm promoter activity, DNA fragments of the p14.5 5'-flanking region were ligated in front of the luciferase gene and were transfected into HeLa and HepG2 cells. A minimal promoter between nt -104 and nt +88 relative to the transcription start site was responsible for basal activity. Furthermore, we observed a head-to-head orientation of p14.5 to the gene for the protein subunit of RNase P and MRP ribonucleoproteins (hPOP1). Luciferase assays with fragments of the hPOP1 5'-flanking region revealed a minimal promoter between nt -20 and nt +98 relative to the start of transcription. These data indicate that the 102 bp region between p14.5 and hPOP1 can act as a bidirectional promoter. The p14.5-hPOP1-cluster was mapped to chromosome 8q22 using in situ hybridization technique.

Noncoding control region of naturally occurring BK virus variants: sequence comparison and functional analysis

The human polyomavirus BK (BKV) has a proven oncogenic potential, but its contribution to tumorigenesis under natural conditions remains undetermined. As for other primate polyomaviruses, the approximately 5.2 kbp double-stranded circular genome of BKV has three functional regions: the coding regions for the two early (T, t antigens) and four late (agno, capsid proteins; VP1-3) genes separated by a noncoding control region (NCCR). The NCCR contains the origin of replication as well as a promoter/enhancer with a mosaic of cis-acting elements involved in the regulation of both early and late transcription. Since the original isolation of BKV in 1971, a number of other strains have been identified. Most strains reveal a strong sequence conservation in the protein coding regions of the genome, while the NCCR exhibits considerable variation between different BKV isolates. This variation is due to deletions, duplications, and rearrangements of a basic set of sequence blocks. Comparative studies have proven that the anatomy of the NCCR may determine the transcriptional activities governed by the promoter/enhancer, the host cell tropism and permissivity, as well as the oncogenic potential of a given BKV strain. In most cases, however, the NCCR sequence of new isolates was determined after the virus had been passaged several times in more or less arbitrarily chosen cell cultures, a process known to predispose for NCCR rearrangements. Following the development of the polymerase chain reaction (PCR), it has become feasible to obtain naturally occurring BKV NCCRs, and their sequences, in samples taken directly from infected human individuals. Hence, the biological significance of BKV NCCR variation may be studied without prior propagation of the virus in cell culture. Such variation has general interest, because the BKV NCCRs represent typical mammalian promoter/enhancers, with a large number of binding motifs for cellular transacting factors, which can be conveniently handled for experimental purposes. This communication reviews the naturally occurring BKV NCCR variants, isolated and sequenced directly from human samples, that have been reported so far. The sequences of the different NCCRs are compared and analyzed for the presence of proven and putative cellular transcription factor binding sites. Differences in biological properties between BKV variants are discussed in light of their aberrant NCCR anatomies and the potentially modifying influence of transacting factors.

The US-1 element from the gene encoding rat poly(ADP-ribose) polymerase binds the transcription factor Sp1

By comparing the upstream DNA sequence of the rat and human genes encoding poly(ADP-ribose) polymerase (PARP), we have defined a 16-bp conserved region and designated it as US-1 for 'upstream sequence 1'. This element is homologous to the recently described binding site for the transcription factor Sp1 in the promoter sequence of the mouse p12 gene which encodes a protease inhibitor. Analyses in gel mobility shift assays revealed that a nuclear protein, produced by all tissue-culture cells tested, specifically binds the US-1 element. The pattern of shifted DNA protein complexes obtained was strikingly similar to that for Sp1, which is supported by the positive displacement of these complexes by an oligomer containing the Sp1 binding site in gel shift competition experiments. Replacement of the Sp1 binding site from the basal promoter of the mouse p12 gene by the rPARP US-1 element did not result in any significant variations in the level of expression of the chloramphenicol acetyltransferase (CAT) reporter gene upon transient transfection of tissue-culture cells. However, when point mutations are introduced in the US-1 element in a similar substitution experiment, a significant reduction in CAT gene expression could be observed. These data are consistent with Sp1 interacting with the US1 element. Results from DNase I footprinting experiments clearly indicated that purified Sp1 not only binds to the US-1 element but also to four other closely located cis-acting sites scattered in the promoter of the rat PARP gene, therefore suggesting that Sp1 is likely to modulate strongly the expression of that gene in different tissues.

Combinatorial crosstalk of transacting factors binding to the L-type pyruvate kinase promoter elements analysed in vitro

Five Dnase 1 footprints, termed boxes L1 to L5, have been characterized in the 280 bp upstream from the cap site of the L-type pyruvate kinase (L-PK) gene. They bind from 3' to 5', the factors HNF1, HNF4, MLTF, and a non-identified protein referred to as L5 binding factor (L5-BF). These elements, individually or variably combined, were tested by cell-free transcription. The L1 box stimulates both L-PK and TK promoters, but in the context of L-PK promoter, it cooperates with the L3 element to reach a high level of transcriptional activation. The L3 and L4 elements exhibit weaker influences, increased by homologous or heterologous interactions. The L5 box behaves as a promoter-dependent negative regulatory element.

Differential expression of the transfected liver-specific alpha 1-inhibitor III gene in normal hepatocytes and hepatoma cells in culture

Normal and malignant hepatocytes were transfected during log phase culture with a nested series of DNA plasmids containing 5'-flanking regions of the rat liver-specific acute phase plasma proteinase alpha 1-inhibitor III (alpha 1 I3) gene. Under these conditions, luciferase reporter gene expression in primary adult rat and mouse hepatocytes was 10-fold higher than luciferase expression in hepatoma lines (human HepG2 and Hep3B; rat FAZA). Optimal expression in primary rat hepatocytes required regions stretching 2214 bp 5'-upstream of the transcription start site. Shorter 5'-flanking sequences were optimal for expression in hepatoma cells (-1025 and -186 bp for rat and human lines, respectively) and primary mouse hepatocytes (-225 bp). In contrast, regions from -186 to -225 bp drove luciferase expression in primary rat hepatocytes, but only 20-75% of optimal levels. Qualitative differences were unaccounted for by non-equivalent uptake of plasmid DNA, suggesting that tissue specific gene expression is regulated differently in normal and malignant cells, and with apparent species specificity.