Biochemical characterization and developmental behavior of Artemia embryonic and nauplial deoxyribonucleases

Regulation of promoter occupancy during activation of cryptobiotic embryos from the crustacean Artemia franciscana

Artemia franciscana embryos can suspend their development and metabolism at the gastrula stage to enter a state of cryptobiosis, forming cysts. Embryonic development and metabolism can be resumed under favorable environmental conditions to give rise to free-swimming larvae or nauplii. The mechanisms that mediate these processes are not completely known. Here, we report our studies of the mechanisms that regulate transcriptional activation upon exiting cryptobiosis. Regulatory regions of several A. franciscana gene promoters were identified. Functional analyses in mammalian cells allowed the identification of transcriptional activator regions in the Actin302 promoter and in promoter 2 of the sarco/endoplasmic reticulum Ca(2+)-ATPase-encoding gene. These regions were shown to specifically bind protein factors from nuclear extracts of A. franciscana nauplii by means of electrophoretic mobility shift assays. Several protein-binding regions were also detected by DNase I protection analysis in the promoters of the genes encoding the alpha1 subunit of Na(+)/K(+)-ATPase, actin 302 and sarco/endoplasmic reticulum Ca(2+)-ATPase. Specific DNA-binding proteins in nauplius nuclear extracts were detected for all the promoter regions analyzed. These proteins were either not present in cyst nuclear extracts or were present in much smaller concentrations. Three of the five regions analyzed also bound proteins present in cyst nuclear extracts. These data indicate that transcriptional activation upon exiting cryptobiosis in A. franciscana involves the expression/activation of DNA-binding transcription factors that are not present in cyst nuclei

Shrimp hepatopancreatic deoxyribonuclease--purification and characterization as well as comparison with bovine pancreatic deoxyribonuclease

Deoxyribonuclease (DNase), isolated from shrimp hepatopancreas by chromatography on DEAE-cellulose, Sephadex G-100, phenyl-Sepharose and hydroxyapatite, is homogeneous as shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The metal ion requirements and the pH-activity optima of shrimp DNase are very similar to those of bovine DNase. Both shrimp and bovine DNases are sensitive to iodoacetate inactivation under the same condition. The active shrimp DNase molecule is a monomer of Mr 44,000, approx. 13,000 larger than the Mr of bovine DNase. Shrimp DNase is rich in glutamic acid, glycine and half-cystine. The single polypeptide chain of shrimp DNase is highly cross-linked by 18 disulfides as compared to only two disulfides in bovine DNase. In contrast to bovine DNase, shrimp DNase is not a glycoprotein, is devoid of the activity against p-nitrophenyl phenylphosphonate (a synthetic substrate for bovine DNase), and resists to inactivation by beta-mercaptoethanol or trypsin under the Ca2(+)-free condition at pH 8. Shrimp DNase shows an isoelectric point of 4.06 on the thin-layer isoelectric focusing and rapidly loses its activity at pH below 5.

Properties of the clot assay, an easy quantitative assay of DNA endonucleases

A systematic examination of the properties of the clot assay, a highly sensitive and simple method to detect DNase activities, is presented. It is shown that it is both quantitative and specific for monitoring the double-strand cleavage of DNA produced by specific and nonspecific endonucleases. Its simplicity and ease of quantification, which exceeds that of other methods of similar sensitivity, indicates that the clot assay can be advantageous in monitoring the activity of both types of endonucleases, especially if carried out in parallel with other more informative assays on the mechanism of action of the enzymes. As an example of its use, it is shown that pancreatic DNase I is capable, in the absence of external metal addition, of a limited attack on DNA containing bound divalent cations.