Descripción: Background: Eukaryotic DNA methylation is one of the most studied epigenetic processes, as it results in a direct and heritable covalent modification triggered by external stimuli. In contrast to mammals, plant DNA methylation, which is stimulated by external cues exemplified by various abiotic types of stress, is often found not only at CG sites but also at CNG (N denoting A, C or T) and CNN (asymmetric) sites. A genome-wide analysis of DNA methylation in Arabidopsis has shown that CNN methylation is preferentially concentrated in transposon genes and non-coding repetitive elements. We are particularly interested in investigating the epigenetics of plant species with larger and more complex genomes than Arabidopsis, particularly with regards to the associated alterations elicited by abiotic stress.Results: We describe the existence of CNN-methylated epialleles that span Asr1, a non-transposon, protein-coding gene from tomato plants that lacks an orthologous counterpart in Arabidopsis. In addition, to test the hypothesis of a link between epigenetics modifications and the adaptation of crop plants to abiotic stress, we exhaustively explored the cytosine methylation status in leaf Asr1 DNA, a model gene in our system, resulting from water-deficit stress conditions imposed on tomato plants. We found that drought conditions brought about removal of methyl marks at approximately 75 of the 110 asymmetric (CNN) sites analysed, concomitantly with a decrease of the repressive H3K27me3 epigenetic mark and a large induction of expression at the RNA level. When pinpointing those sites, we observed that demethylation occurred mostly in the intronic region.Conclusions: These results demonstrate a novel genomic distribution of CNN methylation, namely in the transcribed region of a protein-coding, non-repetitive gene, and the changes in those epigenetic marks that are caused by water stress. These findings may represent a general mechanism for the acquisition of new epialleles in somatic cells, which are pivotal for regulating gene expression in plants. © 2011 González et al; licensee BioMed Central Ltd.

Descripción: 1. 1. The inactivation of phosphorylase a phosphatase decreased the maximum velocity of the phosphorylase a to phosphorylase b conversion reaction when it was assayed at different phosphorylase a concectrations. 2. 2. Maximal phosphorylase a phosphatase activities were found between pH 8 and 8.3. Inactivation of the phosphorylase a phosphatase led to a decrease in the activity in all the pH ranges tested. 3. 3. Theophylline and caffeine stimulated the phosphorylase a phosphatase. The effect of these substances was exerted in the reaction assay of the enzyme. 4. 4. ATP, ADP, AMP, GTP, UTP, CTP and pyrophosphate were found to decrease the rate of the reaction catalyzed by phosphorylase a phosphatase. This effect showed a striking parallelism with the capacity of these compounds to stimulate the phosphatase inactivation. © 1970.

Descripción: 1. 1. The incubation of the pegion breast muscle homogenate at 37° resulted in a time-dependent decrease in phosphatase activity. This effect was stimulated by ATP, ADP, AMP, GTP, UTP, CTP or pyrophosphate. 2. 2. Reactivation of an inactive phosphorylase a phosphatase preparation was obtained by incubation with ATP-Mg2+. Phosphocreatine-Mg2+ or Mg2+ were also found to be effective in bringing about the reactivation of the enzyme. 3. 3. 3′,5′-Cyclic AMP decreased the yield of the active enzyme when it was added either at the beginning or during the activation reaction. © 1970.

Descripción: Background: Premature ovarian failure (POF) is characterized by hypergonadotropic amenorrhoea before the age of 40. Inhibin α-subunit (INHα) gene is proposed as a candidate gene due to its role in negative feedback control of FSH. Methods: Polymorphism -16 C>T of INHα gene was studied in 61 POF patients and 82 controls above 40 years old (C > 40). Substitution 769G>A was studied in 59 POF patients, 76 C > 40 and 73 controls below 40 years old (C < 40). Results: No significant difference in risk of POF development for -16T allele was found when comparing idiopathic POF (I-POF) with C > 40 (Odds ratio = 1.46; 95% confidence interval = 0.63-3.19). Implication of -16C>T polymorphism in serum inhibin levels was analysed in 46 controls, and no significant differences (P > 0.05) were found between CC and CT + TT genotype groups when comparing either mid-follicular phase Pro-αC and inhibin B values or mid-luteal phase Pro-αC and inhibin A values. Heterozygosity for substitution 769G>A was found in 1 of 59 POF woman, 2 of 76 C > 40 and 6 of 73 C < 40. Presence of this su bstitution in a relevant number of control subjects is herein described for the first time. Conclusion: Our results indicate that -16C>T and 769G>A variants in INHα gene may not be associated to POF disease. © 2006 Oxford University Press.

Descripción: Background: A partial deficiency in Protoporphyrinogen oxidase (PPOX) produces the mixed disorder Variegate Porphyria (VP), the second acute porphyria more frequent in Argentina. Identification of patients with an overt VP is absolutely important because treatment depends on an accurate diagnosis but more critical is the identification of asymptomatic relatives to avoid acute attacks which may progress to death. Methods: We have studied at molecular level 18 new Argentinean patients biochemically diagnosed as VP. PPOX gene was amplified in one or in twelve PCR reactions. All coding exons, flanking intronic and promoter regions were manual or automatically sequenced. For RT-PCR studies RNA was retrotranscripted, amplified and sequenced. PPOX activity in those families carrying a new and uncharacterized mutation was performed. Results: All affected individuals harboured mutations in heterozygous state. Nine novel mutations and 3 already reported mutations were identified. Six of the novel mutations were single nucleotide substitutions, 2 were small deletions and one a small insertion. Three single nucleotide substitutions and the insertion were at exon-intron boundaries. Two of the single nucleotide substitutions, c.471G>A and c.807G>A and the insertion (c.388+3insT) were close to the splice donor sites in exons 5, 7 and intron 4 respectively. The other single nucleotide substitution was a transversion in the last base of intron 7, g.3912G>C (c.808-1G>C) so altering the consensus acceptor splice site. However, only in the first case the abnormal band showing the skipping of exon 5 was detected. The other single nucleotide substitutions were transversions: c.101A>T, c.995G>C and c.670 T>G that result in p.E34V, p.G332A and W224G aminoacid substitutions in exons 3, 10 and 7 respectively. Activity measurements indicate that these mutations reduced about 50% PPOX activity and also that they co-segregate with this reduced activity value. Two frameshift mutations, c.133delT and c.925delA, were detected in exons 3 and 9 respectively. The first leads to an early termination signal 22 codons downstream (p.S45fsX67) and the second leads to a stop codon 5 codons downstream (p.I309fsX314). One reported mutation was a missense mutation (p.G232R) and 2 were frameshift mutations: c.1082insC and 1043insT. The last mutation was detected in six new apparently unrelated Argentinean families. Conclusion: Molecular analysis in available family members revealed 14 individuals who were silent carriers of VP. Molecular techniques represent the most accurate approach to identify unaffected carriers and to provide accurate genetic counselling for asymptomatic individuals. The initial screening includes the insertion search. © 2008 Rossetti et al; licensee BioMed Central Ltd.