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DNA topoisomerase II is an enzyme that specializes in DNA disentanglement. It catalyzes the interconversion of DNA between different topological states. This event requires the passage of one duplex through another one via a transient double-strand break. Topoisomerase II is able to process any type of DNA, including structures such as DNA juxtapositions (crossovers), DNA hairpins or cruciforms, which...
Eukaryotic DNA topoisomerase I is active in transcribed chromatin domains to modulate transcription-generated DNA torsional tension. Camptothecin and other agents targeting DNA topoisomerase I are used in the treatment of human solid cancers with significant clinical efficacy. Major progress has been achieved in recent years in the understanding of enzyme structures and basic cellular functions of...
The Avi.groEL intron of Azotobacter vinelandii, which interrupts the termination codon of the groEL gene, is shown to belong to a monophyletic subset of bacterial group II introns that share a large insertion at their 5′ extremity and a peculiar genetic localization. Some of these introns are inserted within, right next to, or very close to, a stop codon while others are located immediately 3′ of,...
Local DNA melting is integral to fundamental processes such as replication or transcription. In vivo, these two processes do not occur on molecules free in solution but, instead, involve DNA molecules which are organized into DNA/proteins complexes. Atomic force microscopy imaging offers a possibility to look at individual molecules. It allowed us to follow the progress of local denaturation in liquid,...
Many genes involved in metabolic processes are regulated by glucocorticoids and/or cyclicAMP. The hepatic expression of the urea cycle enzyme carbamoylphosphate-synthetase-I gene (CPS) is regulated at the transcriptional level by both factors. Here, we report that the 5′ half of the distal enhancer is necessary and sufficient for full cyclicAMP responsiveness. The cyclicAMP-responsive element (CRE),...
In order to further advance our knowledge of the role epidermal growth factor (EGF) plays in thyroid carcinoma, we investigated its effect on the regulation of matrix metalloproteinase-9 (MMP-9), a key enzyme that plays an important role in tumor invasion and angiogenesis. The expression of MMP-9 in EGF-treated and untreated human follicular thyroid carcinoma cells (FTC-133) was evaluated using reverse...
Ribosomal protein L12 is the only component present in four copies in the ribosome. In prokaryotes as well as in yeast and human mitochondria, all copies correspond to the same RPL12. By contrast, we present here evidence that plant mitochondria contain four different RPL12 proteins. Compared to E. coli RPL12, the four mature RPL12 variants show a conserved C-terminal region that contains all the...
The Tat system has the remarkable capacity of exporting proteins in folded conformation across the cytoplasmic membrane. The functional Tat translocase from Gram-negative bacteria consists of TatA, TatB and TatC proteins. To gain information about the species specificity of the Tat translocase, we cloned tat genes from Gram-negative pathogens Shigella flexneri 2a str. 301, Vibrio cholerae El Tor N16961,...
Human skin fibroblasts efficiently internalize the matrikine decorin by receptor-mediated endocytosis, however, very little is known about its intracellular trafficking routes up to lysosomal degradation. In an in vitro system measuring uptake and degradation of [ 35 S]sulfate-labeled decorin, endocytosis was blocked by 46% when clathrin assembly/disassembly was inhibited using chlorpromazine...
DNA polymerase from hyperthermophilic bacteria can elongate tandem repetitive oligoDNA with a complete or incomplete palindromic sequence under isothermal conditions by “hairpin elongation”. However, the product of the reaction has not yet been sufficiently characterized. Here, I demonstrate that when palindromic repetitive oligoDNA, e.g., (5′AGATATCT3′) 6 , was added as a “seed” to the DNA...
Metabolic pathways exhibit structures resulting from an evolutionary process. Pathways have been inherited through time with modification, from the earliest periods of life. It is possible to compare the structure of pathways as done in comparative anatomy, i.e. for inferring ancestral pathways or parts of it (ancestral enzymatic functions), using standard phylogenetic reconstruction. Thus a phylogenetic...
l-Lysine cyclodeaminase from Streptomyces pristinaespiralis was heterologously expressed in Escherichia coli, isolated to 90% purity after two purification steps and characterised. The size of the isolated recombinant enzyme was in agreement with the theoretical size calculated from the corresponding gene. We demonstrated that our preparation converts l-lysine to l-pipecolic acid (enantiomeric excess...
3T3-F442A and BFC-1 cells are widely used for studying adipocyte differentiation and metabolism. Macrophage markers were previously reported in these cell lines. We examined whether 3T3-F442A and BFC-1 would produce interferon-γ (IFN-γ), the expression of which is a matter of debate in cells other than T-lymphocytes and natural killer cells, like macrophages or dendritic. IFN-γ was absent from preadipocytes...
The exosome is a complex of eleven subunits in yeast, involved in RNA processing and degradation. Despite the extensive in vivo functional studies of the exosome, little information is yet available on the structure of the complex and on the RNase and RNA binding activities of the individual subunits. The current model for the exosome structure predicts the formation of a heterohexameric RNase PH...
The phosphotriesterase PTE, identified in the soil bacterium Pseudomonas diminuta, is thought to have evolved in the last several decades to degrade the pesticide paraoxon with proficiency approaching the limit of substrate diffusion (k cat /K M of 4×10 7 M −1 s −1 ). It belongs to the amidohydrolase superfamily, but its evolutionary origin remains obscure....
The protein phosphatase type-1 catalytic subunit (PP1c) does not exist freely in the cell and its activity must be very strictly controlled. Several protein inhibitors of PP1c have been described including the classical mammalian inhibitor-1 (I-1) and inhibitor-2 (I-2). Association of these inhibitors with PP1c appears to involve multiple contacts and in the case of I-2 no less than five I-2 interaction...
Ten new defensins have been isolated from seeds of Triticum kiharae and related species of the Triticum and Aegilops genera by a combination of chromatographic procedures including affinity-, size-exclusion, and reversed-phase high-performance liquid chromatography. Nine were completely sequenced and shown to represent a family of closely related peptides with highly conserved amino acid sequences...
We screened the inhibitor of mouse inosine 5′-monophosphate dehydrogenase (IMPDH) type II from natural compounds, and found that a fatty acid, linoleic acid (C18:2), inhibited IMPDH activity. In the C18:2 fatty acid derivatives, all trans-configuration (i.e., linoelaidic acid), ester form, alcohol form, and addition of the hydroxyl group of linoleic acid had no effect on inhibitory activity. Therefore,...
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