Biological chemistry Hoppe-Seyler最新文献

Cytosine methylation at CpG sites is often negatively correlated with mammalian gene activity. Many transcription factors whose DNA binding site contains one or more CpG dinucleotides are no longer able to efficiently bind DNA when the site is methylated. A notable exception is the zinc finger factor Sp1 which binds DNA and activates transcription even when its binding site is methylated. Here we show that two other zinc finger factors, MTF-1 and Krox-20, can also bind to CpG methylated sites. MTF-1 regulates metallothionein gene transcription by binding to a number of metal responsive elements (MREs), and Krox-20 regulates Hox genes during hindbrain segmentation. However, a refined analysis of MTF-1/MRE binding shows that methylation is not tolerated at every binding site: the highest affinity site in the mouse metallothionein I gene, MREd, is unaffected by methylation, while two other MRE sites with CpGs at different positions are rendered partially or completely nonfunctional by methylation. Both methylation sensitive and insensitive factors/binding sites are likely to determine the developmental expression pattern of a gene.

The nuclease resistance of an oligonucleotide sequence that was phosphorothioate (PS)-modified in various positions and patterns was examined. We present a new ¿minimal' protection strategy for antisense oligonucleotides which is a combination of the end-capping technique and the protection of internal pyrimidine residues which are the major sites of endonuclease degradation. This strategy reduces the number of modifications needed to make a nuclease resistant oligonucleotide and therefore should minimize the non-sequence-specific effects that are frequently observed with uniformly modified oligonucleotides.

The serpins illustrate the way in which the study of a protein family as a whole can clarify the functions of its individual members. Although the individual serpins have become remarkably diversified by evolution they all share a common structural pathology. We have previously shown how plotting of the dysfunctional natural mutations of the serpins on a template structure defines the domains controlling the mobility of the reactive centre loop of the molecule. Here we compare these natural mutations with reciprocal mutations in recombinants that restore the inhibitory stability of a labile member of the family, plasminogen activator inhibitor-1 (PAI-1). The combined results emphasise the critical part played by residues involved in the sliding movement that opens the A-sheet to allow reactive loop insertion. It is concluded that changes in these residues provide the prime explanation for the ready conversion of PAI-1 to the inactive latent state. The consistency of the overall results gives confidence in predicting the likely consequences of mutations in individual serpins. In particular the two common polymorphic mutations present in human angiotensinogen are likely to affect molecular stability and hence may be contributory factors to the observed association with vascular disease.

The effect of anisoosmolarity on the abundance of various mRNA species was examined in perfused rat liver and H4IIE rat hepatoma cells. Hyperosmotic exposure (385 mosmol/l) of isolated rat livers increased mRNA levels for tyrosine aminotransferase (TAT) by 246% and those for phosphoenolpyruvate carboxykinase (PEPCK) by 186%, whereas hypoosmotic exposure (225 mosmol/l) decreased their levels to 43% and 42%, respectively. mRNA levels for fructose-1,6-bisphosphatase (FBP), argininosuccinate lyase (ASL), argininosuccinate synthetase (ASS), glutamine synthetase (GS), glutaminase (GA) and glucokinase (GK) were largely unaffected. In H4IIE cells the modulation of TAT and PEPCK mRNA levels by anisoosmotic exposure was similar to that found in perfused rat liver. ASL and glutaminase mRNA levels were influenced in an opposite manner. The effects of anisoosmolarity on PEPCK mRNA levels in H4IIE cells were largely abolished in the presence of the protein kinase inhibitors H-7, H-89 and HA-1004. Other protein kinase inhibitors such as Go-6850, KN-62, Rp-8-CPT-cAMPS, rapamycin, wortmannin, genistein or herbimycin did not prevent the osmosensitivity of PEPCK mRNA levels. Also pertussis and cholera toxin, vanadate and colchicine did not affect the osmosensitivity of PEPCK mRNA levels. The data suggest that anisoosmotic exposure acts on the levels of some but not all mRNA species and that this action may involve changes in protein phosphorylation. They further indicate that the recently identified osmosensitive signal transduction pathway which involves a G-protein and tyrosine kinase dependent activation of mitogen-activated protein kinases is apparently not involved in the osmoregulation of PEPCK mRNA levels.

Components of the tissue kallikrein-kinin system include tissue kallikrein, kallistatin (kallikrein-binding protein), kininogen, kinin, bradykinin B1 and B2 receptors, and kininases. Tissue kallikrein is a serine proteinase which is capable of cleaving kininogen substrate to release the vasoactive kinin peptide. The binding of kinin to its specific receptor at target organs can produce a wide spectrum of biological effects. Kinin generation is primarily determined by the activity and availability of kallikrein since the level of kininogen is not a rate-limiting factor. Kallikrein levels are controlled by its rate of synthesis, activation, inactivation and clearance. The synthesis of tissue kallikrein is regulated transcriptionally, and its activity is regulated through post-translational processing and inactivation by inhibitors. Kallistatin is a newly discovered serine proteinase inhibitor (serpin) which forms a specific and covalently-linked complex with tissue kallikrein. Kallistatin may regulate tissue kallikrein's activity, bioavailability and clearance rate at the post-translational level. The major site of kallistatin synthesis is the liver with lower expression levels in the pancreas and kidney. Unlike many other serpins which are only present in the plasma, kallistatin is found in various tissues, cells and bodily fluids. The fact that both tissue kallikrein and kallistatin are widely distributed in tissues suggests kallistatin's role as a potential regulator of kallikrein outside the circulation. Protein purification and molecular cloning techniques have been used to study the structure, regulation and function of the components of the kallikrein-kinin system and for exploring their roles in ion transport, inflammation and blood pressure regulation. Considerable progress has been made in recent years to achieve these goals. This article provides an overview of the biochemical properties and potential physiological and pathophysiological roles of kallistatin.

Genetic isolates are the result of some type of bottleneck in the history of a population, revealing the consequences of the founder effect and genetic drift on the population's gene pool. In human populations, isolation is suspected based on an exceptional geographic location or cultural history or on the prevalence of relatively rare genetic diseases. The concept of 'Finnish disease heritage' is well established in the literature, but solid data have only recently emerged regarding the uniformity of disease mutations at the molecular level in this population: for many Finnish diseases for which the molecular defect has been uncovered, over 90% of disease alleles carry the same causative mutation. This suggests dramatic isolation, especially in some subregions of the sparsely populated country. In Finland, this molecular information can be combined with the exceptional genealogical data offered by a well established church record system which dates back to 1640, containing detailed information on births, deaths, marriages and movements of the majority of the population. This provides excellent opportunities for special study designs for the identification not only of rare disease genes but also of major loci which contribute to complex diseases. The utilization of linkage disequilibrium and the search for shared haplotypes can be justified in subpopulations and patient materials from this genetic isolate. This review summarizes the current molecular evidence for genetic isolation as well as the utilization of some special strategies in the disease gene hunt in the Finnish population.

In the axonemes of Tetrahymena cilia, beta-tubulin was digested more rapidly by chymotrypsin than alpha-tubulin. On the other hand, in the solubilized state, both tubulins were digested by the protease at almost the same rate. Among alpha-tubulin isotypes within the axonemes, alpha 5-tubulin was more rapidly digested by chymotrypsin than other alpha-tubulin isotypes. The addition of ATP and vanadate (Vi) to the axonemes significantly protected the alpha 5-isotype from chymotryptic proteolysis. These tendencies could not be observed in tubulins solubilized from axonemes. Based on the case of the alpha 5-tubulin isotype, it is possible to negate the idea that all tubulin isotypes are distributed homogeneously and play similar functional roles within the axonemes.

A high concentration of hop latent viroid (HLVd) was detected in infected mericlones of Osvald's hops grown in vitro. This concentration was about 8-fold higher than in leaves of young, field-grown plants, reaching about 30 pg/mg of fresh mass. Treatment of these in vitro-grown plants at high temperature (35 degrees C) for two weeks lead to a dramatic (about 70-90%) decrease of HLVd content. More detailed investigations performed with mericlone 6147 of Osvald 31 showed that HLVd levels decrease gradually during subsequent cycles of heat treatment. A nuclease activity capable of cleaving HLVd and fully double-stranded RNA was shown to increase significantly in hop tissues during thermotherapy cycles, or after the heat shock. The nuclease activity was found to have similar properties to those extracted earlier from tobacco anthers. This enzyme resembles a sugar-unspecific nuclease which has a maximum activity at pH 5.5. Analysis of the activity with viroid and dsRNA showed that both, endo- and exonucleolytic activities were attributable to the enzyme. A strong tissue-specific gradient of viroid (the lowest level in stem apex and the highest level in roots) was observed in young plants, showing a negative correlation with the dsRNAse activity. In senescent plants, the highest viroid concentration was observed in maturated cones and in upper stems. High nuclease activity in the upper stem tissue suggests that viroid RNA must be protected in this tissue against degradation.

The content and distribution of gangliosides, and total lipid content, were studied in human milk samples from different periods of lactation. We found a significant correlation (r = 0.5564; p = 0.0165) between ganglioside and total lipid contents. There was a selective change in the relative concentrations of GD3 and GM3 during lactation. The most abundant ganglioside in samples from the first three weeks of lactation was GD3, whereas after the first month, GM3 was the major ganglioside. In addition to GD3 and GM3, previously known to be present in human milk, we detected several previously unreported highly polar gangliosides.

We have identified boar sperm membrane components recovered by affinity chromatography on a porcine zona pellucida affinity column. The major zona pellucida-bound proteins were spermadhesins AWN and AQN-3, the heparin-binding protein pAIF, and a homolog of the mouse milk fat globule membrane protein. All these proteins are phospholipid-binding proteins peripherally associated with the plasma membrane. Our data suggest that coating proteins tightly bound to the external lipid bilayer may act as major zona pellucida-binding molecules. Using a synthetic peptide approach we show that the regions of spermadhesin AWN comprising residues 6-12 and 104-108 possess affinity for phosphorylethanolamine. These two amino acid sequences are in close proximity in the predicted structural model for AWN, and in opposite location to its carbohydrate-recognition domain. Taken together, our data provide further evidence for the possible involvement of members of the porcine spermadhesin protein family in gamete interaction and suggest a model for the ultrastructural disposition of functional domains of spermadhesin AWN bound to the sperm surface.