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G Pontecorvo

Publications and source records attributed to G Pontecorvo.

16 recordsLinked to original sources
PubMed2000

A novel repeated sequence DNA originated from a Tc1-like transposon in water green frog Rana esculenta.

We have identified and characterized a highly repetitive family, called R.e./Tc1 in the genome of the green water frog Rana esculenta. This family consists of tandemly repeated sequences, localized at the centromeric regions of chromosomes as shown by Southern blot and 'in situ' hybridization. The repeat unit contains a residue of a Tc1-like transposon by Haematobia irritans fly, bordered by two short direct repeats of 9 bp. Tc1 remnant lays near a sequence identical to Homo sapiens Werner syndrome gene stretch. These sequence data suggest that R.e./Tc1 element was probably originated from a transposition event and a duplication via DNA mechanism of the R.e./Tc1 unit that could give rise to the observed tandem array.

Animals↗
PubMed2000

Novel methylation at GpC dinucleotide in the fish Sparus aurata genome.

To date, vertebrate DNA has been found methylated at the 5' position of cytosine exclusively in dinucleotide CpG or CpNpG stretches. On the the other hand, we determined that cytosine was methylated unusually in dinucleotide GpC at 5'-GGCC-3' sequences in the teleost Sparus aurata EcoRI satellite DNA family. This finding is the first example of methylated GpC sequences in the eukaryotic genomes. At this regard, we have examined the relative methylation levels at this site of the highly repetitive EcoRI satellite DNA family from Sparus aurata different tissues. The EcoRI repeat was remarkably more methylated in male germ cells but hypomethylated in female germ cells at the Hae III restriction site (GpC). The novel modification and the differential methylation pattern suggest that EcoRI satellite could have a structural and/or functional role at the centromeres of Sparus aurata.

Animals↗
PubMed1999

Identification of a new gene encoding pericentromeric dodeca-satellite binding protein in Drosophila melanogaster.

Dodeca-satellite (CCCGTACTCGGT)n is a type of tandemly repeated DNA sequence located in the pericentromeric region of the third chromosome of Drosophila melanogaster and that cross-hybridizes with DNA from other species such as Arabidopsis, mouse and human. This evolutionary conservation suggests that dodeca-satellite might play an important role in the centromeric function. Therefore, the aim of our research was the isolament of genes encoding proteins that might help stabilize these DNA structures, in vivo. To identify D. melanogaster sequence DNAs encoding dodeca-satellite binding proteins, we used the in vivo yeast assay, known as 'one-hybrid system'. Here, we identified a novel gene sequence that encoded pericentromeric dodeca-satellite binding protein and described its sequence characteristics.

Amino Acid Sequence↗
PubMed1998

Variability of DNA methylation pattern in somatic and germ cells in male newt (Amphibia, Urodela) Triturus cristatus carnifex.

In a survey of several mammalian genomes, namely humans, rodents and bovines, the differences in the 5-methylcytosine (m5C) content show that repeated DNA sequences from sperm were undermethylated and from various somatic tissues were heavily methylated. This report shows a pattern of methylation in male newt (Amphibia, Urodela) Triturus cristatus carnifex (T. c. c.) unlike that so far described by other authors in mammals. Using methylation sensitive and insensitive enzymes (HpaII and MspI) and successive 3' terminal labelling (fill-in), we found a greater degree of DNA methylation in premeiotic germ and sperm cells compared to somatic tissue such as hepatocytes. Furthermore the degree of total DNA methylation in spermatozoa appears somewhere between premeiotic germ cells and somatic tissue. Blot hybridization shows that two highly conserved repetitive sequences in amphibian T. c. c., pTvm1 and pTvm8, contribute significantly to the degree of DNA methylation, suggesting a function for these sequences, such as a role in transcriptional regulation.

Animals↗
PubMed1992

Induced crossing-over in Drosophila melanogaster germ cells of DNA repair-proficient and repair-deficient (mei-9L1) males following larval feeding with 5-azacytidine and mitomycin C.

The effects of 5-azacytidine (5-AZ) and mitomycin C (MMC), administered by larval feeding, on crossing-over were measured in Drosophila melanogaster male germ cells of a DNA repair-proficient and a repair-deficient (mei-9L1) strain. Both 5-AZ and MMC are effective inducers of male crossing-over. The estimated number of induced recombination events was higher in repair-proficient than in mei-9L1 males. The apparently lower sensitivity of mei-9L1 males to crossing-over induction may be the result of an incomplete crossing-over process.

Animals↗
PubMed1986

Effects of various metabolites on two phosphoglucomutase allozyme activities from Drosophila melanogaster.

The effects of various metabolites on the two most common phosphoglucomutase allozymes (PGMA and PGMB) in Drosophila melanogaster have been investigated in vitro. 2,3-Diphosphoglycerate (2,3DPG) inhibited PGMA and PGMB to the same degree in the presence of 25 microM glucose-1,6-diphosphate (G1,6P2). However a higher concentration of G1,6P2 partially reversed the inhibition of PGMA exerted by 2,3DPG, so that in the presence of 150 microM G1,6P2 the inhibition of PGMA was half that of PGMB at pH 6.0. Glycerol-3-phosphate (G3P) had no significant effect at pH 7.4 but exerted an activating effect at pH 6.0 which was more pronounced in the case of PGMB. ATP, citrate, and fructose-1, 6-diphosphate (F1,6P2) inhibited both PGMA and PGMB. The differences found in vitro between these two allozymes can have a significant impact on in vivo function and, therefore, on the maintenance of PGM polymorphism in experimental populations of D. melanogaster studied in the laboratory.

Alleles↗
PubMed1977

Cell fusion.

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Cell Fusion↗
PubMed1975

Production of mammalian somatic cell hybrids by means of polyethylene glycol treatment.

Polyethylene glycol (PEG) is known to promote fusion of plant protoplasts. Various adaptations of this treatment to mammalian, including human, cell cultures are reported here. PEG is very effective in producing hybrids capable of indefinite multiplication even in cases, such as early passage human skin fibroblasts and lymphocytes, known to be highly recalcitrant to other treatments.

Animals↗