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Biomedical subjects

G Carrara

Publications and source records attributed to G Carrara.

At least 19 recordsLinked to original sources
PubMed1997

Death and Transfiguration of a Triple Junction in the South Atlantic

Three major lithospheric plates-Antarctic, South American, and African-meet in the South Atlantic near Bouvet Island where the Mid-Atlantic Ridge (MAR), the Southwest Indian Ridge (SWIR), and the American Antarctic Ridge converge toward a fast evolving triple junction. A major magmatic pulse has recently built a new, swollen segment of the SWIR (Spiess Ridge) that is propagating toward the MAR at a rate of 4 to 5 centimeters per year, disrupting a former ridge-ridge-ridge (RRR) triple junction. A new triple junction will be established about 70 kilometers to the north when the propagating SWIR/Spiess segment will impact with the MAR, probably within the next 1 million years. The American Antarctic Ridge will take advantage of the MAR/SWIR duel by capturing an approximately 70-kilometer stretch of MAR, whereas the Antarctic plate will increase its size.

Journal Article↗
PubMed1995

Two helices plus a linker: a small model substrate for eukaryotic RNase P.

Using precursor tRNA molecules to study RNA-protein interactions, we have identified an RNA motif recognized by eukaryotic RNase P (EC 3.1.26.5). Analysis of circularly permuted precursors indicates that interruptions in the sugar-phosphate backbone are not tolerated in the acceptor stem, in the T stem-loop, or between residues A-9 and G-10. Prokaryotic RNase P will function with a minihelix consisting of the acceptor stem connected directly to the T stem-loop. Eukaryotic RNase P cannot use such a minimal substrate unless a linker sequence is added in the gap where the D stem and anticodon stem-loop were deleted.

Animals↗
PubMed1994

Suppression of juvenile chronic myelogenous leukemia colony growth by interleukin-1 receptor antagonist.

Bone marrow (BM) and peripheral blood (PB) cells from patients with juvenile chronic myelogenous leukemia (JCML) exhibit spontaneous in vitro proliferation. Several cytokines including granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 beta (IL-1 beta), and tumor necrosis factor alpha (TNF alpha) have been implicated in supporting the growth of leukemic monocyte-macrophage colonies either by autocrine or paracrine pathways. In seven untreated JCML patients, we investigated the role of IL-1 in the spontaneous growth of these cells by specifically blocking IL-1 receptors. The IL-1 receptor antagonist (IL-1 Ra) was added to the clonogenic assays, and in each case significant (mean = 63%, range = 35% to 82%) inhibition of spontaneous proliferation was observed. Uncultured circulating cells from PB or BM of four out of five patients expressed IL-1 beta-specific mRNA and secreted the protein into the culture supernatants. Moreover, by means of reverse transcriptase-polymerase chain reaction (RT-PCR), we demonstrated that most of the spontaneously growing leukemic colony-forming unit cells (CFU-C) obtained from BM cells of two patients were positive for the presence of the IL-1 beta-specific mRNA. Despite the presence of a measurable amount of GM-CSF in JCML cell culture supernatants, GM-CSF-specific mRNA in CFU-C cells of four cases was not detected by RT-PCR. These data further support a central role for IL-1 beta in the pathogenesis of JCML and suggest that the use of IL-1 Ra could represent a novel therapeutic strategy against this disorder.

Adult↗
PubMed1991

An RNA molecule copurifies with RNase P activity from Xenopus laevis oocytes.

Utilizing a procedure for the purification of RNase P from Xenopus laevis germinal vesicle (GV) extracts, according to which the contamination by a large, cytoplasmic, cylindrical structure (1) is avoided, we demonstrate that the X.laevis enzyme, like the HeLa RNase P, is precipitated by anti-Th antibodies and an RNA molecule (XL RNA), 320 nucleotides long, copurifies with the activity. The sequence of XL RNA is 60% homologous to HeLa H1 RNA, therefore the two molecules seem related.

Animals↗
PubMed1989

Site selection by Xenopus laevis RNAase P.

Investigation of the mechanism of cleavage site selection by Xenopus RNAase P reveals that the acceptor stem, a 7 bp helix common to all tRNA precursors, is required for cleavage. We propose that Xenopus RNAase P recognizes conserved features of the mature tRNA and that the cleavage site is selected by measuring the length of the acceptor stem. In support of this, we demonstrate that insertion of 2 bp in the acceptor stem of yeast pre-tRNA(3Leu) relocates the cleavage site 2 bases 3' to the original one. In addition, insertion of 1 bp in the acceptor stem of the end-matured yeast pre-tRNA(Phe) generates an RNAase P cleavage site: the enzyme produces a mature tRNA with the characteristic 7 bp stem and releases one 5' flanking nucleotide. Since it has previously been shown that cleavage sites of the splicing endonuclease are determined by the length of the anticodon stem, RNAase P and the splicing endonuclease apparently use different stems to determine their cutting sites.

Animals↗
PubMed1981

Selective in vitro transcription of one of the two Alu family repeats present in the 5' flanking region of the human epsilon-globin gene.

The sequence of 2965 nucleotides 5' of the human epsilon-globin gene has been completed. It includes two Alu family repeats present in an inverted configuration. Only the one located farthest from the gene was active as template for RNA polymerase III in a transcription system prepared from nuclei of Xenopus laevis oocytes. This selective transcription may be explained by the lack of homology of the first 45 nucleotides of the non transcribed repeat with other members of the Alu family. In fact this region includes one of the homology blocks described for other RNA polymerase III templates.

Animals↗
PubMed1981

Deletion of the 3' half of the yeast tRNA-Leu3 gene does not abolish promotor function in vitro.

The promotor function of the 3' and 5' half tRNA sequences in the yeast tRNA-Leu3 gene has been studied by in vitro transcription in Xenopus laevis germinal vesicle (GV) extracts. Truncation of the DNA template within the tRNA intervening sequence by Hpa I abolishes transcription. However, separation of the tRNA gene halves by insertion of a 300 bp DNA fragment at the Hpa I site does not affect the promoter efficiency. Further, the complete sequence of the 3' half of the tRNA is not necessary for promoter function, because removal of the 3' half of the gene by cleavage with Pvu II, within the DNA inserted at the Hpa I site, does not inhibit transcription.

Animals↗
PubMed1979

Separation of RNA transcription and processing activities from X. laevis germinal vesicles.

A procedure suitable for en masse preparation of germinal vesicles (GV) from X.laevis oocytes (Scalenghe et al., 1978) has been adapted for studies of transcription. Extracts from GV contain activities for transcription of tRNA genes and for processing the transcription product. The two activities have been separated by column chromatography. One fraction allows synthesis of tRNA precursor molecules in the presence of X.laevis RNA polymerase III. Another fraction contains the activity that cuts and splices those precursors which contain an intervening sequence. Transcription occurs faithfully on linear DNA fragments.

Animals↗
PubMed1977

Purification of a DNA-binding protein from Xenopus laevis unfertilized eggs.

A DNA-binding protein from Xenopus laevis unfertilized eggs has been purified to apparent homogeneity. It is a heat stable, lysine-rich protein and has a molecular weight corresponding to 8,200 daltons, measured by sodium dodecyl sulphate gel electrophoresis. The protein, which is active in a monomeric form, stimulates DNA polymerase alpha, and binds to single and double stranded DNA. One egg contains about 4 x 10(12) molecules (minimum estimate) of the protein; since we calculate that 4 x 10(8) molecules are sufficient to cover the entire genome (haploid complement), there is much more protein than is needed to cover chromosomal DNA.

Amino Acids↗