Project description:This model is described in the article: Kinetics of histone gene expression during early development of Xenopus laevis. Koster JG, Destrée OH and Westerhoff HV. J Theor Biol. 1988 Nov 21;135(2):139-67. PMID: 3267765 Abstract: Using literature data for transcriptional and translational rate constants, gene copy numbers, DNA concentrations, and stability constants, we have calculated the expected concentrations of histones and histone mRNA during embryogenesis of Xenopus laevis. The results led us to conclude that: (i) for X. laevis the gene copy number of the histone genes is too low to ensure the synthesis of sufficient histones during very early development, inheritance from the oocyte of either histone protein or histone mRNA (but not necessarily both) is necessary; (ii) from the known storage of histones in the oocyte and the rates of histone synthesis determined by Adamson and Woodland (1977), there would be sufficient histones to structure the newly synthesized DNA up to gastrulation but not thereafter (these empirical rates of histone synthesis may be underestimates); (iii) on the other hand, the amount of H3 mRNA recently observed during early embryogenesis (Koster, 1987, Koster et al., 1988) could direct a higher and sufficient synthesis of H3 protein, also after gastrulation. We present a quantitative model that accounts both for the observed H3 mRNA concentration as a function of time during embryogenesis and for the synthesis of sufficient histones to structure the DNA throughout early embryogenesis. The model suggests that X. laevis exhibits a major (i.e. some 14-fold) reduction in transcription of histone genes approximately 11 hours after fertilization. This reduction could be due to a decrease in the number of transcribed histone genes, a decreased rate constant of transcription with continued transcription of all the histone genes, and/or a reduction in the time during the cell cycle in which histone mRNA synthesis takes place. Alternatively, the histone mRNA stability might decrease approximately 16-fold 11 hours after fertilization. This model originates from BioModels Database: A Database of Annotated Published Models. It is copyright (c) 2005-2011 The BioModels.net Team. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information. In summary, you are entitled to use this encoded model in absolutely any manner you deem suitable, verbatim, or with modification, alone or embedded it in a larger context, redistribute it, commercially or not, in a restricted way or not.. To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.

Project description:Histone posttranslational modifications (HPTMs) are involved in regulating the synthesis of fungal bioactive compounds. The exact molecular mechanisms of the silencing/activation of secondary metabolism (SM) clusters by these epigenetic events however are not yet fully understood. This work applies a combined approach of quantitative mass spectrometry (LC-MS/MS) and chromatin immunoprecipitation coupled with massive parallel sequencing (ChIP-seq) to identify the chromatin landscape in two metabolic states: primary and secondary metabolism. Furthermore, to link the particular chromatin states to the expression of condition specific genes, genome wide transcriptome (RNA-seq) was performed. Strikingly, we found that silent A. nidulans SM clusters are free of repressive H3K9me3 though this heterochromatic mark forms distinguished peaks flanking the many SM clusters. In addition, silent SM clusters do not contain detectable levels of activating histone marks such as H3K4me3, H3K36me3 or H3Ac, which, to some extent, are established upon activation of the clusters. In order to investigate the function of dynamic H3K4 methylation/demethylation in transcription, we characterized the KdmB- Jarid1 family histone demethylase. The in vitro assay using heterologously expressed KdmB showed that it is an active demethylase; moreover, MS/MS as well ChIP-seq approaches revealed that it targets H3K4me3 in vivo mediating transcriptional repression. KdmB positively regulates the expression of 40% of A. nidulans SM genes and this function appears to be independent of its demethylase activity. Our bioinformatics approach revealed two states of H3K4me3 in A. nidulans genome: loci with low levels of this mark are more disposed to differential expression in response to environmental clues, while the genes marked by high H3K4me3 levels are constitutively transcribed in our experimental conditions. Taken together our data reveal important role of H3K4 methylation/demethylation in transcription regulation. Furthermore, this study presents the first genome-wide map of H3K4me3, H3K9me3, H3K36me3 and H3Ac in A. nidulans in different metabolic conditions. Two strains, wild type and kdmB deletion, at two conditions, growth at primary (17h) and secondary (48h), were analysed. Each sample was replicated.

Project description:Histone posttranslational modifications (HPTMs) are involved in regulating the synthesis of fungal bioactive compounds. The exact molecular mechanisms of the silencing/activation of secondary metabolism (SM) clusters by these epigenetic events however are not yet fully understood. This work applies a combined approach of quantitative mass spectrometry (LC-MS/MS) and chromatin immunoprecipitation coupled with massive parallel sequencing (ChIP-seq) to identify the chromatin landscape in two metabolic states: primary and secondary metabolism. Furthermore, to link the particular chromatin states to the expression of condition specific genes, genome wide transcriptome (RNA-seq) was performed. Strikingly, we found that silent A. nidulans SM clusters are free of repressive H3K9me3 though this heterochromatic mark forms distinguished peaks flanking the many SM clusters. In addition, silent SM clusters do not contain detectable levels of activating histone marks such as H3K4me3, H3K36me3 or H3Ac, which, to some extent, are established upon activation of the clusters. In order to investigate the function of dynamic H3K4 methylation/demethylation in transcription, we characterized the KdmB- Jarid1 family histone demethylase. The in vitro assay using heterologously expressed KdmB showed that it is an active demethylase; moreover, MS/MS as well ChIP-seq approaches revealed that it targets H3K4me3 in vivo mediating transcriptional repression. KdmB positively regulates the expression of 40% of A. nidulans SM genes and this function appears to be independent of its demethylase activity. Our bioinformatics approach revealed two states of H3K4me3 in A. nidulans genome: loci with low levels of this mark are more disposed to differential expression in response to environmental clues, while the genes marked by high H3K4me3 levels are constitutively transcribed in our experimental conditions. Taken together our data reveal important role of H3K4 methylation/demethylation in transcription regulation. Furthermore, this study presents the first genome-wide map of H3K4me3, H3K9me3, H3K36me3 and H3Ac in A. nidulans in different metabolic conditions.

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KdmA, a histone H3 demethylase with bipartite function, differentially regulates primary and secondary in Aspergillus nidulans metabolism

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