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J Sebastián

Publications and source records attributed to J Sebastián.

At least 19 recordsLinked to original sources
PubMed1987

Immunological relationships between Artemia RNA polymerases and between RNA polymerases II from different eukaryotic organisms.

Rabbit antibodies against Artemia RNA polymerase II have been raised and utilized to study the immunological relationships between the subunits from RNA polymerases I, II and III from this organism and RNA polymerase II from other eukaryotes. We describe here for the first time the subunit structure of Artemia RNA polymerases I and III. These enzymes have 9 and 13 subunits respectively. The anti-RNA polymerase II antibodies recognize two subunits of 19.4 and 18 kDa common to the three enzymes, and another subunit of 25.6 kDa common to RNA polymerases II and III. The antibodies against Artemia RNA polymerase II also react with the subunits of high molecular weight and with subunits of around 25 and 33 kDa of RNA polymerase II from other eukaryotes (Drosophila melanogaster, Chironomus thummi, triticum (wheat) and Rattus (rat]. This interspecies relatedness is a common feature of eukaryotic RNA polymerases.

Animals↗
PubMed1986

Satellite DNA in the crustacean Artemia.

We have isolated a satellite fraction from the Artemia genome by both restriction endonuclease digestion and equilibrium density centrifugation in CsCl gradients containing ligand dye Hoechst 33258. Satellite DNA was arranged in long stretches (approx. 23 kb) of tandem repeats of a basic unit of 113 bp. The basic unit has been sequenced, showing a G + C content very close to that of total DNA. Different amounts of satellite were present in several populations of Artemia, whereas it was absent from others.

Animals↗
PubMed1986

Characterization of two types of rRNA gene repeat units from the crustacean Artemia.

We have previously described that Artemia rRNA genes are organized with a basic repeat unit of 16.5 kb [Cruces et al., Biochem. Biophys. Res. Commun. 98 (1981) 404-409]. Here we describe the organization of the DNA coding for rRNA of a different population of this crustacean that has a repeat unit of 12.2 kb. Both types of repeat units have been cloned and the organization of the external spacers studied by restriction analysis. Both external spacers contain repeated sequences, but they are not homologous to each other. Sequences from the external spacer of the 16.5 kb repeat are also found elsewhere in the genome, within sequences not related to rRNA genes.

Animals↗
PubMed1985

Purification and subunit structure of RNA polymerases I and II from Dictyostelium discoideum vegetative cells.

A purification procedure to obtain RNA polymerases I (or A) and II (or B) from Dictyostelium discoideum amoeba has been developed. The enzymes were solubilized from purified nuclei and separated by DEAE-Sephadex chromatography. RNA polymerases I and II were further purified by a second chromatography on DEAE-Sephadex followed by chromatographies on phosphocellulose and heparin-sepharose. The specific activities of purified RNA polymerases I and II are 92 units/mg protein and 70 units/mg protein, respectively. The subunit structure of both RNA polymerases were analyzed by polyacrylamide gel electrophoresis under denaturing conditions after glycerol gradient centrifugation of the enzymes. The putative subunits of RNA polymerase I have molecular weights of 180 000, 125 000, 43 000, 40,000, 34 000, 31 000, 25 000, 19 000, 17 000 and 14 000. The putative subunits of RNA polymerase II have molecular weights of 200 000 (170 000), 130 000, 33 000, 25 000, 19 000, 17 000, 15 000, 13 000. There are three polypeptides with common molecular weight in Dictyostelium RNA polymerases I and II. The subunit of 25 000 daltons of both enzymes has common immunological determinants with RNA polymerase II from crustacean Artemia.

Chromatography, Affinity↗
PubMed1984

Purification and properties of cAMP-independent nuclear protein kinase from Dictyostelium discoideum.

A cyclic-AMP-independent nuclear protein kinase has been purified from Dictyostelium discoideum amoebae. The purification procedure involves chromatography of DEAE-Sephadex, phosphocellulose and heparin-Sepharose. The purified enzyme phosphorylates threonine and serine of acidic proteins as casein and phosvitin. Phosphorylation of casein is stimulated by spermine. The kinase requires Mg2+ and can utilize both ATP and GTP as phosphoryl donors. Heparin is a potent inhibitor of the enzyme, being the protein kinase activity fully inhibited at concentrations of 0.5 micrograms/ml. One polypeptide of molecular mass 38 kDa was the major protein band present in the purified kinase preparation as estimated by NaDodSO4 denaturing polyacrylamide gel electrophoresis. This band belongs to the protein kinase because it is the only one that is observed associated with the protein kinase activity when the enzyme preparation is centrifuged in glycerol gradients. The 38-kDa polypeptide is also the major product of autophosphorylation of the enzyme preparation. The enzymatic properties allow to classify the enzyme as a type-II casein kinase. However, its structural properties are different from the mammalian type-II casein kinases and make the D. discoideum enzyme more similar to the plants type-II casein kinases.

Adenosine Triphosphate↗
PubMed1983

Developmental changes in poly(A) polymerase activity in Artemia.

The levels of poly(A) polymerase activity have been determined during Artemia early development. Poly(A) polymerase activity increases steadily during postgastrular embryonic development reaching a maximum shortly after hatching. The rise of poly(A) polymerase is concomitant with an increase in poly(A) content and with a change in the subcellular distribution of the enzyme activity, the major increase corresponding to the nuclear fraction. Only one isoenzyme of poly(A) polymerase has been identified in Artemia embryos and nauplii despite changes in enzyme levels and subcellular changes during early development. Poly(A) polymerase is not associated with the cytoplasmic poly(A)-containing ribonucleoprotein particles stored in Artemia dormant embryos.

Artemia↗
PubMed1980

Levels of the RNA polymerases during the early larval development of Artemia.

Artemia nauplii contain three forms of RNA polymerase. RNA polymerases I and II have the common pattern of alpha-amanitin sensitivity of the eukaryotic enzymes, but RNA polymerase III is insensitive to high concentrations of the drug. The determination of the levels of the RNA polymerases during early larval development is affected by the increase of proteolytic activity during this stage, which produces the inactivation of RNA polymerases I and III in vitro. Protease B has been identified to be the enzyme responsible for the inactivation of RNA polymerase I. The culture conditions of Artemia larvae also affect the levels of the RNA polymerases. The maintenance of the larvae in the absence of food produces a decrease of RNA polymerases I and III several hours after hatching. In contrast, fed nauplii contain almost stable levels of the three forms of RNA polymerases during the studied period of larval development. The decrease of the levels of RNA polymerases I and III in starved nauplii could be the molecular mechanism responsible for the drop in RNA synthesis observed during the larval development in cultures of nauplii in the absence of an external source of food.

Amanitins↗
PubMed1978

Purification and properties of a ribonuclease induced during the early larval development of Artemia salina.

Dormant gastrulae and developing embryos of the brine shrimp Artemia salina contain very low levels of nuclease activity. During early larval development, there is an induction of ribonuclease which has been partially purified and characterized. The enzyme catalyzes an endonucleolytic cleavage of RNA and has no detectable activity on native or denatured DNA. Among a series of synthetic polynucleotides, poly(U) is hydrolyzed with the highest efficiency and poly(G) is not cleaved by the enzyme. The activity on poly(U) is 100 times higher than on RNA. The enzyme requires Mg2+ or Mn2+ and in inactivated by treatment with chelating agent. The inactive preparations can be reactivated by Ca2+ and Mn2+ but not by Mg2+. The ribonuclease is thermosensitive and has maximal activity at pH 7.5. These properties distinguish the Artemia salina ribonuclease from other eukaryotic ribonucleases already reported. The high activity and specificity of this ribonuclease on poly(U) may suggest a role for this enzyme in the processing of the messenger RNA.

Animals↗