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C Beaumont

Publications and source records attributed to C Beaumont.

At least 19 recordsLinked to original sources
PubMed1992

CfT-I: an LTR-retrotransposon in Cladosporium fulvum, a fungal pathogen of tomato.

A retrotransposon from the fungal tomato pathogen Cladosporium fulvum (syn. Fulvia fulva) has been isolated and characterised. It is 6968 bp in length and bounded by identical long terminal repeats of 427 bp; 5 bp target-site duplications were found. Putative first- and second-strand primer binding sites were identified. Three long open reading frames (ORFs) are predicted from the sequence. The first has homology to retroviral gag genes. The second includes sequences homologous to protease, reverse transcriptase, RNAse H and integrase, in that order. Sequence comparisons of the predicted ORFs indicate that this element is closely related to the gypsy class of LTR retrotransposons. Races of the pathogen exhibit polymorphisms in their complement of at least 25 copies of the sequence. Virus-like particles which co-sediment with reverse transcriptase activity were observed in homogenates of the fungus. This is the first report of an LTR retrotransposon in a filamentous fungus.

Amino Acid Sequence↗
PubMed1992

A second ferritin L subunit is encoded by an intronless gene in the mouse.

Multiple homologous sequences for the ferritin L subunit are present in mammalian genomes, but so far, only one expressed gene has been described. Here we report the isolation of a cDNA from a mouse bone marrow library, corresponding to an isoform of the mouse ferritin L subunit. This new subunit, that we named Lg, differs from the L subunit of ten amino acids. Specific amplification of mouse genomic DNA using the polymerase chain reaction (PCR) confirmed the presence of this Lg sequence in the mouse genome but also suggested that it must be encoded by an intronless gene. Using a series of different Lg-specific oligonucleotides as probes, we subsequently isolated a genomic clone containing an uninterrupted sequence, identical to the Lg cDNA. This Lg gene lacks introns and does not contain the 28 base pairs (bp) conserved motif usually present at the 5' end of most ferritin mRNAs, which confers translational regulation by iron. When transiently transfected into K562 cells, this Lg genomic clone is actively transcribed, suggesting that, although it possesses the characteristics of a processed pseudogene, it is likely to correspond to the gene encoding this new ferritin subunit.

Amino Acid Sequence↗
PubMed1992

Comparison of various characteristics of duration of fertility in hens.

1. Maximum duration (Dm, number of days post-insemination until last fertile egg) and efficient duration (De, number of days post-insemination until first infertile egg) of fertility, number of fertile eggs (F), dead embryos and hatched chicks (H) during the 21 d following the latter of two intravaginal inseminations (with 125 x 10(6) spermatozoa) on two consecutive days were measured in a total of 2549 layer-type hens at three ages (starting at 30, 44 and 55 weeks of age). 2. De and Dm were highly correlated (0.46 less than or equal to r less than or equal to 0.67). Both De and Dm were also well correlated with F (0.45 less than or equal to r less than or equal to 0.80) and H (0.45 less than or equal to r less than or equal to 0.76) whereas correlations between numbers of dead embryos and other variables were very low and often not significant (0.04 less than or equal to r less than or equal to 0.29). 3. The highest repeatabilities between hen ages were observed for F (0.34 less than or equal to r less than or equal to 0.49) and H (0.36 less than or equal to r less than or equal to 0.48) and the lowest for numbers of dead embryos (0.02 less than or equal to r less than or equal to 0.28). 4. Because of low fertility 18 d after insemination, the period over which measurements were made could have been reduced by 3 d without significant differences in the ranking of the females. 5. The number of perivitelline spermatozoa found in eggs laid on day 2 is not a good predictor of duration of fertility but could allow the culling of hens associated with lowest De or Dm.

Animals↗
PubMed1991

Mouse ferritin H sequences map to chromosomes 3, 6, and 19.

Human and rodent genomes contain multiple copies of ferritin H and L subunit sequences, although it is not yet clear whether there is more than one expressed gene for either of these subunits. We have isolated a cDNA corresponding to mouse ferritin H subunit and observed that the mouse genome contains three to four H-related sequences. This cDNA was used to establish the genomic location of mouse ferritin H subunit genes by chromosomal in situ hybridization. Metaphase chromosomes of concanavalin A-stimulated lymphocytes from a WMP male mouse were examined by in situ hybridization with 3H-labeled cDNA and the chromosomes were identified by R banding (fluorochrome-photolysis-Giemsa method). The results indicate that mouse ferritin H-related sequences map at chromosomes 3, 6, and 19. Homology of synteny between human and mouse suggests that the sequence on mouse chromosome 19 corresponds to the structural H gene.

Animals↗
PubMed1991

Mouse ferritin H multigene family is polymorphic and contains a single multiallelic functional gene located on chromosome 19.

Multiple ferritin H subunit sequences are present in the genome of higher vertebrates, but it is not yet known with certainty if more than one is expressed. In this paper, we provide evidence that there is only one functional ferritin H gene in the mouse. We screened a mouse genomic library using a mouse ferritin H cDNA as a probe and characterized five clones. These genomic clones proved to contain three pseudogenes and two allelic forms of a unique functional gene. These two alleles differed by only two point mutations in the promoter and three in the first intron and by a 31-bp insertion in the first intron. They were equally expressed when transiently transfected in HeLa cells. These five genomic clones account for all the bands observed on a Southern blot of mouse genomic DNA hybridized with a ferritin H cDNA, and these bands present a restriction fragment length polymorphism between various representatives of the genus Mus. Using a DNA panel prepared from the backcross progeny (C57BL/6 X Mus spretus)F1 X C57BL/6, we localized the functional ferritin H gene (Fth) in region B of mouse chromosome 19 and established cen-Ly-1-Fth-Pax-2 as the most likely gene order, thus defining a conserved syntenic fragment with human chromosome 11q.

Alleles↗
PubMed1991

Comparison of Henderson's Method I and restricted maximum likelihood estimation of genetic parameters of reproductive traits.

Genetic parameters of simulated reproductive traits were estimated with Henderson's Method I or restricted maximum likelihood (REML). Each of the 25 samples consisted of 2,667 birds from 50 sires. When reproductive traits were measured on all birds, the means of both sets of estimates were equal to the true value; however, precision was higher with REML. When they were only measured on the 60 (20%) heaviest birds, Henderson's Method I was severely biased by selection (up to 40% for estimates of heritability of reproductive traits and up to 45% for estimates of genetic correlation between reproductive traits and body weight). This bias, as well as the variance of estimates, increased with selection rate and absolute value of genetic correlation between body weight and reproductive traits (or another criterion of selection). Conversely, REML was not biased by selection. It should therefore be preferred when sequential selection occurs.

Analysis of Variance↗
PubMed1990

The hepatic biosynthesis of rat thyroxine binding globulin (TBG): demonstration, ontogenesis, and up-regulation in experimental hypothyroidism.

Using a human thyroxine binding globulin (TBG) cDNA probe, we demonstrate that rat liver contains two TBG mRNA species of different length, consisting of about 1.8 Kb and 2.4 Kb respectively. Slot blot analysis of the hepatic mRNAs from rats of different age reveals a fair correlation between the developmental trend of the messengers and that of the TBG circulating levels. Finally Northern blot and slot studies demonstrate that the increase of serum TBG induced in adults by thyroidectomy actually reflects an enhanced hepatic biosynthesis of the protein.

Animals↗
PubMed1989

The mouse porphobilinogen deaminase gene. Structural organization, sequence, and transcriptional analysis.

The porphobilinogen deaminase gene encodes the third enzyme of the heme biosynthetic pathway. This gene is expressed in a tissue-specific manner and gives rise to two isoenzymatic forms encoded by mRNA species differing in their 5' extremity. Recent studies in human demonstrated that the tissue-specific expression of the porphobilinogen deaminase gene is determined in erythropoietic cells, by the utilization of a specific promoter situated 3' to the housekeeping promoter used in other cell types. This results, through differential splicing, in the mutually exclusive presence of either exon 1 or exon 2 in mature mRNAs. Here, we report the cloning and sequencing of the porphobilinogen deaminase gene from mouse. The overall organization of the mouse gene is similar to that of the human one. In the housekeeping promoter, only a short stretch of homology is found including two potential Sp1 binding sites; in contrast, more extensive similarity appears in the erythroid-specific promoter including two motifs also found in globin gene, a CACCC box, and a recently described Ery F1 consensus binding sequence. We derived a set of single-stranded probes corresponding to different parts of the mouse gene to carry out a detailed analysis of the transcriptional unit in various cell types, using a run-on transcription assay on isolated nuclei. In liver cells, the first (non-erythropoietic) exon is more actively transcribed than parts of the gene situated downstream, suggesting that the elongation of transcripts is blocked within the 5' part of the first intron. In erythropoietic cells, the downstream promoter becomes activated; surprisingly, the initiation of transcription is also enhanced from the upstream (housekeeping) promoter and most of the transcripts initiated at the housekeeping promoter stop downstream of the first exon, between the two promoters.

Amino Acid Sequence↗
PubMed1989

A point mutation G----A in exon 12 of the porphobilinogen deaminase gene results in exon skipping and is responsible for acute intermittent porphyria.

We have determined the mutation in a patient with acute intermittent porphyria. The mRNA coding for porphobilinogen deaminase was reverse transcribed then the cDNA was enzymatically amplified in vitro. Upon sequencing of a polymerase chain reaction product of abnormal size we found that this fragment lacked exon 12 of the gene. We analysed a genomic fragment containing exon 12 and determined that the patient was heterozygous for a point mutation G A at the last position of exon 12. We propose that this base change is responsible for an abnormal processing of the mutant allele such that exon 12 is missing in the mature mRNA. The resulting aberrant mRNA encodes a truncated protein which is inactive but stable and can be detected using antibodies directed against the normal enzyme.

Acute Disease↗
PubMed1989

Transcriptional regulation of ferritin H and L subunits in adult erythroid and liver cells from the mouse. Unambiguous identification of mouse ferritin subunits and in vitro formation of the ferritin shells.

Ferritin H and L subunits present cell-specific features of structure, function, and transcriptional regulation. Mouse Friend erythroleukemia cells offer an interesting model to analyze the erythroid-specific expression of ferritin genes for comparison with the liver, an iron-storing tissue. cDNA clones for mouse ferritin H and L subunits have been isolated and sequenced. The two subunits have very similar calculated masses, 20.9 and 20.6 kDa for H and L, respectively. Electrophoretic analysis of the subunits encoded by the cDNA 1) allows unambiguous identification of mouse ferritin subunits; 2) clearly shows that mouse H and L chains can make heteropolymers in vitro; and 3) demonstrates that, at least in vitro, free subunits can coexist with subunits polymerized into complete shells. The mouse ferritin gene family displays a variable degree of complexity, ranging from three homologous sequences for the H genes to 10-14 homologous loci for the L genes. Transcription of ferritin genes exhibits tissue-specific difference. Nuclear transcriptional run-off experiments show that the L gene is more actively transcribed in the liver than in Friend erythroleukemia cells at different stages of maturation. The accumulation of the H subunit mRNA which results from dimethyl sulfoxide induction of Friend cells is the consequence of an increase in the transcription rate of the H gene. However, the H gene mRNA is transcribed at a similar rate in the liver and in induced Friend cells although 5-fold more mRNA accumulates in these cells. Therefore, there is a tissue-specific regulation of mouse ferritin expression at both the transcription and mRNA stability levels.

Animals↗
PubMed1987

Ferritin synthesis in differentiating Friend erythroleukemic cells.

We have investigated the regulation of ferritin synthesis during induction of Friend erythroleukemic cells by dimethyl sulfoxide. Northern blot analysis shows that mouse ferritin H and L mRNAs each contain approximately 1.1 kilobases. The levels of both mRNAs increase after addition of dimethyl sulfoxide in a biphasic manner. After a sharp rise in the first 6 h, the levels decline and then rise again over the next 90 h. These increases in mRNA levels reflect increased transcription of both mRNAs. Analysis of ferritin subunit synthesis surprisingly showed no corresponding increase in the rate of protein synthesis, suggesting that the additional mRNA was not in functional polysomes. These studies also indicated a novel processing of mouse ferritin H subunits. H subunits appear to be synthesized as a precursor of approximately 22,500. This form is not present in mature shells. Pulse-chase experiments indicated that the precursor is first processed to an intermediate form of 20,000 and then to the 18,000 component found in functional shells.

Animals↗
PubMed1987

Tissue-specific expression of porphobilinogen deaminase. Two isoenzymes from a single gene.

Porphobilinogen deaminase (hydroxymethylbilane synthase; EC 4.3.1.8), the third enzyme of the heme biosynthetic pathway, catalyzes the stepwise condensation of four porphobilinogen units to yield hydroxymethylbilane, which is in turn converted to uroporphyrinogen III by cosynthetase. We compared the apparent molecular mass of porphobilinogen deaminase from erythropoietic and from non-erythropoietic cells by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and immune-blotting. The results indicate that two isoforms of porphobilinogen deaminase can be distinguished and differ by 2000 Da. Analysis of cell-free translation products directed by mRNAs from human erythropoietic spleen and from human liver demonstrates that the two isoforms of porphobilinogen deaminase are encoded by distinct messenger RNAs. We cloned and sequenced cDNAs complementary to the non-erythropoietic form of porphobilinogen deaminase encoding RNA. Comparison of these sequences to that of human erythropoietic mRNA [Raich et al. (1986) Nucleic Acids Res. 14, 5955-5968] revealed that the two mRNA species differ by their 5' extremity. From the mRNA sequences we could deduce that an additional peptide of 17 amino acid residues at the NH2 terminus of the non-erythropoietic isoform of porphobilinogen deaminase accounts for its higher molecular mass. RNase mapping experiments demonstrate that the two porphobilinogen deaminase mRNAs are distributed according to a strict tissue-specificity, the erythropoietic form being restricted to erythropoietic cells. We propose that a single porphobilinogen deaminase gene is transcribed from two different promoters, yielding the two forms of porphobilinogen deaminase mRNAs. Our present finding may have some relevance for further understanding the porphobilinogen deaminase deficiency in certain cases of acute intermittent porphyria with an enzymatic defect restricted in non-erythropoietic cells.

Ammonia-Lyases↗
PubMed1987

Porphyria cutanea tarda and HLA-linked hemochromatosis. Evidence against a systematic association.

This study was designed to test the hypothesis that a hemochromatosis allele is implicated in the expression of porphyria cutanea tarda. HLA phenotypes were determined in 69 porphyria cutanea tarda patients, 42 of which had the sporadic type (normal erythrocyte uroporphyrinogen decarboxylase activity) and 27 unrelated patients who had the familial type (diminished erythrocyte uroporphyrinogen decarboxylase activity). The incidence of HLA antigen A3, a marker of the hemochromatosis allele, was identical in the sporadic patients (23.8%), in the familial patients (22.2%), and in the controls (24.5%). Furthermore, no clinical difference could be found between A3 and non-A3 patients. These results demonstrate no systematic association between hemochromatosis and porphyria cutanea tarda in the population studied. Another HLA-linked gene, however, could be implicated in the expression of the disease as HLA antigen DR7 presented an incidence statistically different (p less than 0.05) between sporadic (16.6%) and familial patients (43%).

Adult↗
PubMed1986

Uroporphyrinogen decarboxylase structural mutant (Gly281----Glu) in a case of porphyria.

Uroporphyrinogen decarboxylase deficiency in man is responsible for familial porphyria cutanea tarda and hepatoerythropoietic porphyria. A recent study of a family with hepatoerythropoietic porphyria showed that the enzyme defect resulted from rapid degradation of the protein in vivo. Cloning and sequencing of a complementary DNA for the mutated gene revealed that the mutation was due to the replacement of a glycine residue by a glutamic acid residue at position 281. This base change leads to a protein that is very rapidly degraded in the presence of cell lysate. Characterization of the mutation will allow comparison of this defect in a homozygous patient with defects in other patients with familial porphyria cutanea tarda.

Amino Acid Sequence↗
PubMed1986

Porphobilinogen deaminase is unstable in the absence of its substrate.

Porphobilinogen deaminase is induced during the dimethyl sulfoxide-mediated differentiation of Friend erythroleukemia cells. We have previously shown that when succinylacetone, a potent inhibitor of porphobilinogen formation, is present during the differentiation process, the induction of the enzyme is apparently suppressed. Here, we provide evidence that, in this condition, porphobilinogen deaminase is synthesized normally but does not accumulate as a consequence of an accelerated turnover. The normal half-life of the protein is 24 h but decreases to 10 h when the formation of its substrate is impaired by succinylacetone. We propose that when the enzyme is covalently bound to its substrate, a normal step in this enzymatic reaction, it is protected from proteolytic degradation, and we show that this new finding is relevant to the human disorder acute intermittent porphyria.

Ammonia-Lyases↗