Examinando por Autor "Nardocci, G."
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Ítem Epigenetic regulation of the ribosomal cistron seasonally modulates enrichment of H2A.Z and H2A.Zub in response to different environmental inputs in carp (Cyprinus carpio)(BMC, 2013-07) Simonet, N.; Reyes, M.; Nardocci, G.; Molina, A.; Alvarez, M.Background: The specific deposition of histone variants into chromatin is an important epigenetic mechanism that contributes to gene regulation through chromatin architectural changes. The histone variant H2A.Z is essential in higher eukaryotes, and its incorporation within chromatin is a relevant process for gene expression and genome stability. However, the dual positive and negative roles of H2A.Z in gene regulation still remain unclear. We previously reported that acclimatization in common carp fish (Cyprinus carpio) involves cyclical seasonal gene reprogramming as an adaptation response to its natural environment, when rRNA synthesis and processing are profoundly affected. Epigenetic mechanisms primarily contribute to the transcriptional modulation of ribosomal genes concomitant with the acclimatization process, thus significantly regulating this process. The aim of this study was to describe the presence of several H2A.Z subtypes in carp, and assess the role of H2A.Z on the ribosomal cistron in summer- and winter-acclimatized carp. Results: This paper reports for the first time about the transcriptional expression of four different H2A.Z subtypes belonging to the same organism. Remarkably, a novel H2A.Z.7 was found, which corresponds to a tissue-specific histone subtype that contains seven amino acid residues longer than the canonical H2A.Z. Moreover, H2A.Z enrichment through the ribosomal cistron was significantly higher during summer, when rRNA transcription and processing are highly active, than it was in winter. Similar patterns of H2A.Z enrichment are found in two seasonally active promoters for genes transcribed by RNA polymerase II, the L41 and Δ9- desaturase genes. Interestingly, ubiquitylated-H2A.Z (H2A.Zub) was strongly enriched on regulatory regions of the ribosomal cistron in summer-acclimatized carp. Additionally, H2A.Z was present in both heterochromatin and euchromatin states on ribosomal cistron and RNA polymerase II promoters. Conclusions: Our study revealed seasonally-dependent H2A.Z enrichment for active ribosomal cistron and RNA polymerase II promoters during the carp environmental adaptation. Moreover, seasonal H2A.Zub enrichment appears as a specific mechanism contributing to the regulation of chromatin architecture under natural conditions. The existence of several H2A.Z subtypes in carp suggests that the epigenetic regulation in this species constitutes a complex and finely tuned mechanism developed to cope with seasonal environmental changes that occur in its habitat.Ítem Ezh2-dependent H3K27me3 modification dynamically regulates vitamin D3-dependent epigenetic control of CYP24A1 gene expression in osteoblastic cells(Wiley-Liss Inc., 2020-01) Moena, D.; Nardocci, G.; Acevedo, E.; Lian, J.; Stein, G.; Stein, J.; Montecino, M.Epigenetic control is critical for the regulation of gene transcription in mammalian cells. Among the most important epigenetic mechanisms are those associated with posttranslational modifications of chromosomal histone proteins, which modulate chromatin structure and increased accessibility of promoter regulatory elements for competency to support transcription. A critical histone mark is trimethylation of histone H3 at lysine residue 27 (H3K27me3), which is mediated by Ezh2, the catalytic subunit of the polycomb group complex PRC2 to repress transcription. Treatment of cells with the active vitamin D metabolite 1,25(OH)2D3, results in transcriptional activation of the CYP24A1 gene, which encodes a 24-hydroxylase enzyme, that is, essential for physiological control of vitamin D3 levels. We report that the Ezh2-mediated deposition of H3K27me3 at the CYP24A1 gene promoter is a requisite regulatory component during transcriptional silencing of this gene in osteoblastic cells in the absence of 1,25(OH)2D3. 1,25(OH)2D3 dependent transcriptional activation of the CYP24A1 gene is accompanied by a rapid release of Ezh2 from the promoter, together with the binding of the H3K27me3-specific demethylase Utx/Kdm6a and thereby subsequent erasing of the H3K27me3 mark. Importantly, we find that these changes in H3K27me3 enrichment at the CYP24A1 gene promoter are highly dynamic, as this modification is rapidly reacquired following the withdrawal of 1,25(OH)2D3. © 2020 Wiley Periodicals, Inc.Ítem Genome sequencing and transcriptomic analysis of the Andean killifish Orestias ascotanensis reveals adaptation to high-altitude aquatic life(Elsevier, 2022-01) Di Genova, A.; Nardocci, G.; Maldonado-Agurto, R.; Hodar, Ch.; Valdivieso, C.; Valdivieso, C.; Morales, P.; Gajardo, F.; Marina, R.; Gutiérrez, R.; Orellana, A.; Cambiazo, V.; Cambiazo, V.; González, M.; Glavic, A.; Mendez, M.; Maass, A.; Allende, M.; Montecino, M.Orestias ascotanensis (Cyprinodontidae) is a teleost pupfish endemic to springs feeding into the Ascotan saltpan in the Chilean Altiplano (3,700 m.a.s.l.) and represents an opportunity to study adaptations to high-altitude aquatic environments. We have de novo assembled the genome of O. ascotanensis at high coverage. Comparative analysis of the O. ascotanensis genome showed an overall process of contraction, including loss of genes related to G-protein signaling, chemotaxis and signal transduction, while there was expansion of gene families associated with microtubule-based movement and protein ubiquitination. We identified 818 genes under positive selection, many of which are involved in DNA repair. Additionally, we identified novel and conserved microRNAs expressed in O. ascotanensis and its closely-related species, Orestias gloriae. Our analysis suggests that positive selection and expansion of genes that preserve genome stability are a potential adaptive mechanism to cope with the increased solar UV radiation to which high-altitude animals are exposed to.