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U Hansen

Publications and source records attributed to U Hansen.

At least 55 records · Page 3Linked to original sources
PubMed1994

Mapping and mutagenesis of the amino-terminal transcriptional repression domain of the Drosophila Krüppel protein.

We previously demonstrated that the Drosophila Krüppel protein is a transcriptional repressor with separable DNA-binding and transcriptional repression activities. In this study, the minimal amino (N)-terminal repression region of the Krüppel protein was defined by transferring regions of the Krüppel protein to a heterologous DNA-binding protein, the lacI protein. Fusion of a predicted alpha-helical region from amino acids 62 to 92 in the N terminus of the Krüppel protein was sufficient to transfer repression activity. This putative alpha-helix has several hydrophobic surfaces, as well as a glutamine-rich surface. Mutants containing multiple amino acid substitutions of the glutamine residues demonstrated that this putative alpha-helical region is essential for repression activity of a Krüppel protein containing the entire N-terminal and DNA-binding regions. Furthermore, one point mutant with only a single glutamine on this surface altered to lysine abolished the ability of the Krüppel protein to repress, indicating the importance of the amino acid at residue 86 for repression. The N terminus also contained an adjacent activation region localized between amino acids 86 and 117. Finally, in accordance with predictions from primary amino acid sequence similarity, a repression region from the Drosophila even-skipped protein, which was six times more potent than that of the Krüppel protein in the mammalian cells, was characterized. This segment included a hydrophobic stretch of 11 consecutive alanine residues and a proline-rich region.

Amino Acid Sequence↗
PubMed1994

One exon of the human LSF gene includes conserved regions involved in novel DNA-binding and dimerization motifs.

The transcription factor LSF, identified as a HeLa protein that binds the simian virus 40 late promoter, recognizes direct repeats with a center-to-center spacing of 10 bp. The characterization of two human cDNAs, representing alternatively spliced mRNAs, provides insight into the unusual DNA-binding and oligomerization properties of LSF. The sequence of the full-length LSF is identical to that of the transcription factors alpha CP2 and LBP-1c and has similarity to the Drosophila transcription factor Elf-1/NTF-1. Using an epitope-counting method, we show that LSF binds DNA as a homodimer. LSF-ID, which is identical to LBP-1d, contains an in-frame internal deletion of 51 amino acids resulting from alternative mRNA splicing. Unlike LSF, LSF-ID did not bind LSF DNA-binding sites. Furthermore, LSF-ID did not affect the binding of LSF to DNA, suggesting that the two proteins do not interact. Of three short regions with a high degree of homology between LSF and Elf-1/NTF-1, LSF-ID lacks two, which are predicted to form beta-strands. Double amino acid substitutions in each of these regions eliminated specific DNA-binding activity, similarly to the LSF-ID deletion. The dimerization potential of these mutants was measured both by the ability to inhibit the binding of LSF to DNA and by direct protein-protein interaction studies. Mutations in one homology region, but not the other, functionally eliminated dimerization.

Alternative Splicing↗
PubMed1994

Lack of ultrasonographic evidence for severe hepatosplenic morbidity in schistosomiasis mansoni in Mali.

The inhabitants of four villages endemic for Schistosoma mansoni in central Mali (n = 1,106 of both sexes, age range 2-80 years) and of two nonendemic villages in another part of the country were examined parasitologically and ultrasonographically to establish the prevalence of periportal liver fibrosis (PF) and other features of hepatosplenic schistosomiasis. The prevalence of S. mansoni infection ranged from 36% to 93% in the endemic villages. A severe infection (> 400 eggs/g of stool) was found in 16% of the infected individuals. No case of grade III PF (echogenic bands usually > 10 mm in diameter around the central part and major branches of the portal vein and streak-like fibrous bands that extended into the periphery of the liver) and only eight cases of grade II PF (echogenic bands usually > 10 mm in diameter around the central part and major branches of the portal vein) were found; no other signs of severe hepatosplenic disease were encountered. However, grade I PF (echogenic bands usually > 4 mm in diameter that were best visible in the area of the portal vein bifurcation and gall bladder neck) was detected in 21% of all individuals, mainly in adults. In the nonendemic villages, the prevalence of grade I PF in adults was 9%. Generally, there was no significant correlation between the grade of PF and S. mansoni egg output. In one village with a high endemicity level, however, the prevalence of grade PF I increased with the intensity of infection. Morphometric data revealed no significant influence of S. mansoni infection on portal vein stem diameter and spleen size.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Erythema elevatum diutinum: case report showing an unusual distribution.

A case of erythema elevatum diutinum showing an unusual distribution is reported. Hard nodules were located on the patient's fingertips and pulps while the extensor surfaces were not involved. The disease was initially misinterpreted based on both clinical and histologic examination. Dapsone therapy was followed by a remarkable recovery. The clinical and histologic features of erythema elevatum diutinum are summarized.

Aged↗
PubMed1993

Selective repression of transcriptional activators at a distance by the Drosophila Krüppel protein.

The Krüppel (Kr) protein, bound at kilobase distances from the start site of transcription, represses transcription by RNA polymerase II in mammalian cells. Repression is monotonically dependent on the dose of Kr protein and the presence of Kr binding site(s) on the DNA. These data suggest an inhibitory protein-protein interaction between the Kr protein and proximal transcription factors. Repression by Kr depends on the specific activator protein driving transcription. In particular, Kr protein selectively represses transcription mediated by the Sp1 glutamine-rich activation domain, tethered to the promoter by a GAL4 DNA-binding domain, but does not repress transcription stimulated by the acidic GAL4 activator. We believe this represents repression by a quenching interaction between DNA-bound Kr protein and the activation region of Sp1, rather than competition between Sp1 and Kr for a limiting transcriptional component. Selective, context-related repression affords an added layer of combinatorial control of gene expression by sequence-specific transcription factors.

Animals↗
PubMed1993

Association of nucleosome-free regions and basal transcription factors with in vivo-assembled chromatin templates active in vitro.

Using SV40 minichromosomes assembled in vivo, we have studied the relationship between a nucleosome-free promoter-region and initiation of transcription by RNA polymerase II on chromatin templates in vitro. Our data suggest that accessibility of DNA to transcription factors, programmed into the structure of the chromatin, is crucial for initiation of transcription. First, minichromosomes competent to be transcribed in vitro contained nucleosome-free promoter regions. Second, tsC219 minichromosomes, most of which contain the nucleosome-free promoter region, supported transcription more efficiently both in vivo and in vitro than wild-type minichromosomes, in which only a subset contain the nucleosome-free region. We have also identified basal transcription factors associated with the in vivo-assembled chromatin templates. A striking correlation was observed between minichromosomes associated with in vivo initiated RNA polymerases and those associated with the basal transcription factors TFIID and TFIIE/F, and to a lesser extent, TFIIB. Of these associated factors, only TFIID was poised for ready assembly into preinitiation complexes and therefore for subsequent initiation of transcription. However, an active chromatin template could also be maintained in the absence of the binding of TFIID. Finally, our data are consistent with the presence of TFIIF in elongating ternary complexes on the chromatin templates.

Animals↗
PubMed1993

Growth response to 4-hydroxy-L-threonine of Escherichia coli mutants blocked in vitamin B6 biosynthesis.

Mutants of Escherichia coli (pdx B and pdx C) which are blocked in the biosynthesis of pyridoxol (vitamin B6) showed a growth response to 4-hydroxy-L-threonine. This observation constitutes the first direct evidence in support of the view that 4-hydroxy-L-threonine is implicated in the biosynthesis of vitamin B6. 1-Aminopropan-2,3-diol, the decarboxylation product of 4-hydroxy-L-threonine, does not support the growth of these mutants. Deuterium from deuterium-labelled 1-aminopropan-2,3-diol was not incorporated into pyridoxol.

Escherichia coli↗
PubMed1993

[Incidence of myocardial infarction in Denmark. Results from Dan-Monica 1982-1984].

The mortality from ischemic heart disease in Denmark has changed from a steady increase towards a decrease also in younger males during the 1980s. During this period, the Glostrup Population Studies have registered the incidence of myocardial infarction, risk factor changes and changes in medical care in Copenhagen county (320,000 inhabitants) as part of WHO MONICA, which compares 39 centres in 26 countries. The incidence of myocardial infarction during the first three years, 1982-1984, of the Heart Register, DAN-MONICA at Glostrup Hospital, is reported. The register is complete and valid. If the age specific incidence of myocardial infarction in Denmark was as in this survey, the results indicate an age standardized incidence for the Danish population including all age groups over the age of 25 of 5.58 per 1000 per year (7.48 per 1000 adult males and 3.99 per 1000 adult females).

Adult↗
PubMed1992

Activation of RNA polymerase II transcription by the specific DNA-binding protein LSF. Increased rate of binding of the basal promoter factor TFIIB.

While the components of the initiation complex at an RNA polymerase II basal promoter have been well characterized, few mechanistic studies have focused on how upstream DNA-binding, transcriptional activators influence protein assembly at the initiation site. Our analysis of basal transcription on both the simian virus 40 and adenovirus major late promoters demonstrates that two slow steps in initiation of transcription are the assembly of the general transcription factors TFIID and TFIIB onto the template DNA. On the simian virus 40 major late promoter, the rate of initiation complex formation is dramatically increased in the presence of the cellular transcriptional activator LSF. Direct analysis by band mobility shift assays demonstrates that LSF has no effect on the rate of binding, or the stability of TFIID on the promoter, predicting that LSF would not affect the template commitment step. Rather, kinetic analyses demonstrate that LSF reduces the lag in the rate of initiation complex formation attributable to the slow addition of TFIIB and suggest that LSF increases the rate of association of TFIIB with the committed template. In addition, LSF increases the total number of transcription complexes in long term assays, which is also consistent with LSF increasing the rate of association of TFIIB, where TFIIB is not saturating. These results indicate a mechanism for the activation of the initiation of RNA polymerase II transcription by one upstream activating protein, LSF. This mechanism may also be applicable to other activators that function in cases where limiting concentrations of TFIIB in the cell dictate slow binding of TFIIB.

Base Sequence↗
PubMed1992

In vitro initiation of transcription by RNA polymerase II on in vivo-assembled chromatin templates.

We have studied the initiation of transcription in vitro by RNA polymerase II on simian virus 40 (SV40) minichromosomal templates isolated from infected cells. The efficiency and pattern of transcription from the chromatin templates were compared with those from viral DNA templates by using two in vitro transcription systems, either HeLa whole-cell extract or basal transcription factors, RNA polymerase II, and one of two SV40 promoter-binding transcription factors, LSF and Sp1. Dramatic increases in numbers of transcripts upon addition of transcription extract and different patterns of usage of the multiple SV40 initiation sites upon addition of Sp1 versus LSF strongly suggested that transcripts were being initiated from the minichromosomal templates in vitro. That the majority of transcripts from the minichromosomes were due to initiation de novo was demonstrated by the efficient transcription observed in the presence of alpha-amanitin, which inhibited minichromosome-associated RNA polymerase II, and an alpha-amanitin-resistant RNA polymerase II, which initiated transcription in vitro. The pattern of transcription from the SV40 late and early promoters on the minichromosomal templates was similar to the in vivo pattern of transcription during the late stages of viral infection and was distinct from the pattern of transcription generated from viral DNA in vitro. In particular, the late promoter of the minichromosomal templates was transcribed with high efficiency, similar to viral DNA templates, while the early-early promoter of the minichromosomal templates was inhibited 10- to 15-fold. Finally, the number of minichromosomes competent to initiate transcription in vitro exceeded the amount actively being transcribed in vivo.

Adolescent↗
PubMed1991

Salpingitis isthmica nodosa in female infertility and tubal diseases.

Salpingitis isthmica nodosa (SIN) is a condition of nodular thickening of the proximal Fallopian tube. The purpose of this study was to investigate the occurrence, distribution and frequency of SIN in Danish women salpingectomized because of tubal pregnancy or salpingitis and to correlate SIN with infertility, pregnancies, outcome of pregnancies, births, pelvic inflammatory disease and salpingitis. Sections from the isthmus were present in the specimens from 223 tubes from 193 patients and were analysed by the same pathologist. Originally, SIN was found in 12 patients but on re-examination, it was found in 24 patients. Ten women with SIN were bilaterally salpingectomized. Only one woman had SIN in both tubes. Women with SIN gave birth to as many children as women without SIN. After SIN had been diagnosed, no children were born, but this was not statistically different from the frequency of births in the non-SIN group after salpingectomy. Women with SIN had histological signs of salpingitis more often than women without SIN, but SIN complicated with salpingitis did not influence the number of children or tubal pregnancies. Women with SIN had a greater risk of two or more tubal pregnancies than women without SIN.

Adult↗
PubMed1991

trans activation of the simian virus 40 late promoter by large T antigen requires binding sites for the cellular transcription factor TEF-1.

Simian virus 40 (SV40) T antigen stimulates the level of transcription from several RNA polymerase II promoters, including the SV40 late promoter. The mechanism of trans activation appears to be indirect since binding of T antigen to specific DNA sequences is not required. However, specific promoter elements that respond to T antigen have not previously been defined. We identified DNA sequences from the SV40 late promoter whose ability to stimulate transcription is induced by the expression of T antigen. In particular, the Sph I + II motifs of the SV40 enhancer can confer T-antigen inducibility to the normally uninducible herpes simplex virus thymidine kinase gene promoter when multiple copies of the sequence are inserted 5' of the transcription initiation site and TATA sequence. Binding sites for the cellular transcription factor TEF-1 and octamer binding proteins are contained within the Sph I + II motifs, as well as at other positions in the SV40 promoter. To study the role of individual protein-binding sites in trans activation by T antigen, mutations were constructed in various TEF-1 and octamer protein-binding sites of the SV40 late promoter. These mutations did not significantly affect basal promoter activity. However, mutation of all three TEF-1 sites prevented detectable activation by T antigen. DNase I footprinting of the mutated promoters with purified proteins demonstrated that inducibility by T antigen correlated with binding affinity of TEF-1 for the DNA and not with binding affinity of an octamer binding protein.

Animals↗
PubMed1990

[Nodular pulmonary amyloidosis].

Amyloidosis limited to the lower respiratory tract is a relatively rare condition. It may be either tracheobronchial or parenchymal, and the parenchymal form may be either nodular or diffuse. A case of nodular pulmonary amyloidosis is presented.

Aged↗
PubMed1990

Feasibility of intracardiac injection of drugs during cardiac arrest.

In a cardiological department (Coronary Care Unit) routine treatment of asystole and electromechanical dissociation has comprised intracardiac injection (ICI) of drugs, usually given by trained nurses, using the parasternal approach into the right ventricle, followed by continued external cardiac massage. A 7-year experience is presented with 543 consecutive ICIs to 247 patients. Cardiac action was restored in half of the patients (125/247); 7.7% (19/247) were discharged alive. Autopsy was done in 80% of fatal cases (182/228). A left-sided pneumothorax was demonstrated in 9 of the 80 patients surviving ICI for greater than 1 h, a minor haemopericardium in three, but serious consequences in none. Lesions of the coronary artery or of the myocardium attributable to the ICI were never seen. Asystole in some patients was converted into ventricular fibrillation or ventricular tachycardia which in six patients proved intractable, but other serious cardiac arrhythmias having a possible connection with the ICI were not observed. It is concluded that during a cardiac standstill, drug treatment by ICI with good technique carries a low risk, quite acceptable in these circumstances, and from a theoretical point of view can be expected to have advantages over administration of the drug into a peripheral vein.

Bicarbonates↗
PubMed1990

Transcription factor LSF binds two variant bipartite sites within the SV40 late promoter.

The HeLa transcription factor LSF has been purified by heparin-agarose and DNA affinity chromatography, and its DNA binding and transcription properties have been characterized. LSF is a 63-kD polypeptide that binds to two distinct bipartite sites within the SV40 promoter region. One binding site consists of GC motifs 2 and 3 within the 21-bp repeats (LSF-GC site), and the other consists of sequences centered 44 bp upstream of the major late initiation site, L325 (LSF-280 site). Four guanine residues within the LSF-GC site, when methylated, strongly interfere with LSF binding. Alteration of the spacing, but not the sequence, between the two directly repeated GC motifs dramatically reduces the binding affinity of LSF for the site. Thus, LSF appears to recognize directly repeated GC motifs, when their center-to-center distance is 10 bp. The LSF-GC and LSF-280 sites share limited sequence homology. Only half of the LSF-280 site contains a short GC-rich sequence homologous to the GC motif. However, the binding affinity of LSF to the two sites is similar. LSF activates transcription from the SV40 late promoter in vitro from initiation site L325, via its binding to the template DNA.

Base Sequence↗
PubMed1990

Surecut 0.6 mm liver biopsy in the diagnosis of cirrhosis.

Liver biopsy with the 0.6 mm (23 gauge) Surecut needle was compared to conventional Menghini biopsy in the diagnosis of cirrhosis. Seventy-seven consecutive patients (mainly alcoholics) with a clinical indication for liver biopsy had both biopsies performed simultaneously. In 71 patients sufficient material for a morphological diagnosis concerning liver architecture was obtained with both biopsy techniques (Surecut insufficient in 5 cases and Menghini insufficient in 2 cases). The biopsies were classified as cirrhosis or non-cirrhosis. There was agreement in 69 cases (97%, confidence limits 90-100%). Using the result of the Menghini biopsy as the final diagnosis, the predictive values for a positive and negative diagnosis for the Surecut needle were 96% and 98%, respectively. There were no complications to either of the biopsies. It is suggested that the 0.6 mm Surecut biopsy may be used in the diagnosis of cirrhosis in cases where conventional Menghini needle biopsy is contraindicated.

Biopsy, Needle↗
PubMed1990

Cavernous haemangioma of the jejunum. Long-standing anaemia in a child.

A 15-year-old boy who had been examined for almost lifelong iron deficiency anaemia caused by occult gastrointestinal bleeding was eventually, by abdominal surgery, found to have a cavernous haemangioma of the jejunum. A diagnostic approach is described and the importance of systematic evaluation and subsequent diagnosis in such patients is stressed.

Adolescent↗