Protein kinase activities during early development of Ascaris suum

Programmed DNA elimination in multicellular organisms

Genetic information typically remains constant in all cells throughout the life cycle of most organisms. However, there are exceptions where DNA elimination is an integral, developmental program for some organisms, associated with generating distinct germline versus somatic genomes. Programmed DNA elimination occurs in unicellular ciliates and diverse metazoa ranging from nematodes to vertebrates. DNA elimination can occur through chromosome breakage and selective loss of chromosome regions or the elimination of individual chromosomes. Recent studies provide compelling evidence that DNA elimination is a novel form of gene silencing, dosage compensation, and sex determination. Further identification of the eliminated sequences, genome changes, and in depth characterization of this phenomenon in diverse metazoans is needed to shed new light on the functions and mechanisms of this regulated process.

Minor participation of cAMP on the protein kinase phosphorylation of mitochondrial and cytosolic fractions from Ascaris suum: a comparative study with porcine heart muscle

In contrast to porcine heart muscle in which cAMP effectively activated the phosphorylation of cytosolic proteins, cAMP exerted a minor effect on the phosphorylation of proteins from the soluble fraction of Ascaris suum muscle. Similarly, cAMP did not enhance the kinase activity in the mitochondrial membranes from porcine heart and A. suum, although major differences in protein phosphorylation were observed between both fractions. However, cAMP-dependent protein kinases (PKA) were evidenced in the parasitic soluble mitochondrial fraction, since the phosphorylation of histone IIA and kemptide was augmented in this fraction, in the presence of cAMP. An increase in the phosphorylation of exogenously added A. suum phosphofructokinase was also obtained when cAMP was added to the parasite soluble mitochondrial fraction. The phosphorylation of phosphofructokinase by this fraction was inhibited when kemptide and cAMP were included in the reaction mixture, suggesting substrate competition for the same PKA. Although PKI (6-22), a reported inhibitor of the catalytic subunit of mammalian cAMP-dependent PKAs, did not affect the endogenous phosphorylation of proteins in the various A. suum fractions, an inhibition on the phosphorylation of exogenously added kemptide and phosphofructokinase was observed when PKI (6-22) was incubated with the parasite mitochondrial soluble fraction.

Ascaris suum: protein phosphotyrosine phosphatases in oocytes and developing stages

Protein tyrosine phosphatases were analyzed in oocytes of Ascaris suum. Phosphatases dephosphorylating modified acidic lysozyme were present in high-molecular-weight form (M(r) > 600,000) and as a 50- to 55-kDa protein in the soluble fraction. The low-molecular-weight form of the phosphatase cross-reacted with an antiserum raised against human T-cell protein tyrosine phosphatase and was not distinguishable from the 50- to 55-kDa protein tyrosine phosphatase previously described in the muscular layer of the adult worms (B. Schmid et al. 1996, Molecular and Biochemical Parasitology 77, 183-192). The low-molecular-weight form was also present on immunoblots of high-molecular-weight protein tyrosine phosphatase preparations after denaturing electrophoresis. The same or a similar form of the tyrosine phosphatase was also found in detergent extracts from the pelletal fraction. In addition, another tyrosine phosphatase of 180 kDa molecular mass that dephosphorylated myelin basic protein was also found in extracts from the soluble compartment as well as in detergent extracts from the pelletal fraction. It showed no cross-reactivity with antisera raised against soluble mammalian phosphatases and was resistant to inhibition by vanadate. While the activities of the myelin basic protein-dephosphorylating protein phosphatase remained fairly constant during early development of the oocytes, the activity of the enzyme dephosphorylating modified lysozyme in the pelletal fraction decreased to less than 10% of the initial activity between days 3 and 28 of incubation. Immunocytochemical studies of unfertilized and developing Ascaris eggs revealed association of protein tyrosine kinase and protein tyrosine phosphatase with the egg shell, in addition to their presence in the neighborhood of mitochondria. The amount of enzyme changed with the stage of development. In the larval stage (21 days) protein tyrosine kinase had increased in the chitin layer of the shell and in the nuclei while the relative amount of tyrosine phosphatase decreased in accordance with the biochemical data.

A novel UV-damaged DNA binding protein emerges during the chromatin-eliminating cleavage period in Ascaris suum

During the early cleavage period of Ascaris suum , chromatin diminution takes place in the somatic founder cells. In the process of chromatin diminution numerous heterochromatic blocks, consisting predominantly of highly repeated DNA, are discarded during mitotic anaphase and are later on digested in the cytoplasm. Very little is known about proteins that are involved in chromatin diminution. We have detected a nuclear protein and purified it to near homogeneity by its preferential binding to UV-damaged DNA. We termed this protein chromatin diminution associated factor 1 (CDAF1), because maximum binding activity per nucleus was observed to develop in 4-8-cell stages, when chromatin diminution occurs for the first time. CDAF1 recognizes cyclobutane pyrimidine dimers in UV-damaged double-stranded DNA. Its binding properties identify CDAF1 as a novel kind of damaged-DNA binding protein. CDAF1 activity is almost not detectable in 1-celled embryos. It increases dramatically during formation of somatic founder cells and persists up to the first larval stage. However, CDAF1 is absent in tissues of adults. These findings led us to suggest that CDAF1 plays a dual role: during the early segregative cleavage period it might be involved in chromatin diminution as a transfactor and act in nucleotide excision repair as an accessory factor throughout embryogenesis.