Project description:LSH/DDM1 enzymes are required for DNA methylation in higher eukaryotes and have poorly defined roles in genome maintenance in yeast, plants, and animals. The filamentous fungus Neurospora crassa is a tractable system that encodes a single LSH/DDM1 homolog (NCU06306). We report that the Neurospora LSH/DDM1 enzyme is encoded by mutagen sensitive-30 (mus-30), a locus identified in a genetic screen over 25 years ago. We show that MUS-30-deficient cells have normal DNA methylation, but are hypersensitive to the DNA damaging agent MMS (methyl methanesulfonate). MUS-30 is a nuclear protein, consistent with its predicted role as a chromatin remodeling enzyme, and levels of MUS-30 are increased following DNA damage. MUS-30 co-purifies with Neurospora WDR76, a homolog of yeast Changed Mutation Rate-1 and mammalian WD40 repeat domain 76. Deletion of wdr76 rescued MMS-hypersensitivity of Dmus-30 strains, demonstrating that the MUS-30-WDR76 interaction is functionally important. DNA damage-sensitivity of Dmus-30 is also partially suppressed by deletion of methyl adenine glycosylase-1, a component of the base excision repair machinery (BER); however, the rate of BER is not affected in Dmus-30 strains. It was reported that mammalian LSH is required for efficient double strand break (DSB) repair. We found that MUS-30-deficient cells were not defective for DSB repair, and we observed a negative genetic interaction between Dmus-30 and Dmei-3, the Neurospora RAD51 homolog required for homologous recombination. These data are consistent with a role for MUS-30 that is independent of DSB repair. Our findings demonstrate that LSH/DDM1 enzymes are key regulators of genome stability in eukaryotes.
Project description:LSH/DDM1 enzymes are required for DNA methylation in higher eukaryotes and have poorly defined roles in genome maintenance in yeast, plants, and animals. The filamentous fungus Neurospora crassa is a tractable system that encodes a single LSH/DDM1 homolog (NCU06306). We report that the Neurospora LSH/DDM1 enzyme is encoded by mutagen sensitive-30 (mus-30), a locus identified in a genetic screen over 25 years ago. We show that MUS-30-deficient cells have normal DNA methylation, but are hypersensitive to the DNA damaging agent MMS (methyl methanesulfonate). MUS-30 is a nuclear protein, consistent with its predicted role as a chromatin remodeling enzyme, and levels of MUS-30 are increased following DNA damage. MUS-30 co-purifies with Neurospora WDR76, a homolog of yeast Changed Mutation Rate-1 and mammalian WD40 repeat domain 76. Deletion of wdr76 rescued MMS-hypersensitivity of Dmus-30 strains, demonstrating that the MUS-30-WDR76 interaction is functionally important. DNA damage-sensitivity of Dmus-30 is also partially suppressed by deletion of methyl adenine glycosylase-1, a component of the base excision repair machinery (BER); however, the rate of BER is not affected in Dmus-30 strains. It was reported that mammalian LSH is required for efficient double strand break (DSB) repair. We found that MUS-30-deficient cells were not defective for DSB repair, and we observed a negative genetic interaction between Dmus-30 and Dmei-3, the Neurospora RAD51 homolog required for homologous recombination. These data are consistent with a role for MUS-30 that is independent of DSB repair. Our findings demonstrate that LSH/DDM1 enzymes are key regulators of genome stability in eukaryotes. crf5-1 isolates (two replicates each from the F1 and F2 generation) were grown in Vogel's minimal medium for 48 hours. As a control, two replicates of the wildtype strain were grown under identical conditions.
Project description:To determine the genes directly and indirectly under the control of the Grainy-head homolog (GHH) transcription factor in Neurospora crassa Three different sample types (Aerial Hyphae & Conidia; Mycelia; or Whole Colonies) of both wild-type (FGSC #2489) and grainy-head homolog (FGSC #13563) strains of Neurospora crassa were subjected to transcriptome analyses to determine the genes differentially expressed in the ghh background compared to wild type.
Project description:To determine the genes directly and indirectly under the control of the Grainy-head homolog (GHH) transcription factor in Neurospora crassa
Project description:Eukaryotic DNA methylation is found in silent transposable elements and active genes. Nucleosome remodelers of the DDM1/Lsh family are thought to be specifically required to maintain transposon methylation, but the reason for this is unknown. Here, we find that a chromatin gradient that extends from the most heterochromatic transposons to euchromatic genes determines the requirement of DDM1 for methylation maintenance in all sequence contexts. We also show that small RNA-directed DNA methylation (RdDM) is inhibited by heterochromatin and absolutely requires the nucleosome remodeler DRD1. DDM1 and RdDM independently mediate nearly all transposon methylation, which is catalyzed by the methyltransferases MET1 (CG), CMT3 (CHG), DRM2 (CHH) and CMT2 (CHH), and collaborate to repress transposition and regulate the methylation and expression of genes. Our results indicate that the Arabidopsis genome is defined by a heterochromatic continuum that governs the access of DNA methyltransferases and potentially all DNA binding proteins. Examination of DNA methylation, transcription and nucleosomes in Arabidopsis wild-type and/or ddm1, RdDM and DNA methylase mutants.
Project description:Eukaryotic DNA is wrapped around histone octamers to form nucleosomes, which are separated by linker DNA bound by histone H1. In many species, the DNA exhibits methylation of CG dinucleotides, which is epigenetically inherited via a semiconservative mechanism. How methyltransferases access DNA within nucleosomes remains mysterious. Here we show that methylation of nucleosomes requires DDM1/Lsh nucleosome remodelers in Arabidopsis thaliana and mouse. We also show that removal of histone H1, which partially restores methylation in ddm1 mutants, does so primarily in the linker DNA between nucleosomes. In h1ddm1 compound mutants, substantial portions of the genome exhibit dramatically periodic methylation that approaches wild-type levels in linker DNA but is virtually absent in nucleosomes. We also present evidence that de novo methylation supplements semiconservative maintenance of CG methylation across generations. Overall, our results demonstrate that nucleosomes and H1 are barriers to DNA methylation, which are overcome by DDM1/Lsh nucleosome remodelers.
Project description:Eukaryotic DNA methylation is found in silent transposable elements and active genes. Nucleosome remodelers of the DDM1/Lsh family are thought to be specifically required to maintain transposon methylation, but the reason for this is unknown. Here, we find that a chromatin gradient that extends from the most heterochromatic transposons to euchromatic genes determines the requirement of DDM1 for methylation maintenance in all sequence contexts. We also show that small RNA-directed DNA methylation (RdDM) is inhibited by heterochromatin and absolutely requires the nucleosome remodeler DRD1. DDM1 and RdDM independently mediate nearly all transposon methylation, which is catalyzed by the methyltransferases MET1 (CG), CMT3 (CHG), DRM2 (CHH) and CMT2 (CHH), and collaborate to repress transposition and regulate the methylation and expression of genes. Our results indicate that the Arabidopsis genome is defined by a heterochromatic continuum that governs the access of DNA methyltransferases and potentially all DNA binding proteins.
Project description:Purpose: We utilised high-throughput genomic approache to investigate transcriptional changes in two Neurospora strains (74A [wild-type] and mutant Δmus-52), under different phosphate availability conditions to evaluate the effects of mus-52 deletion in gene transcriptional modulation, and thus, infer its influence regarding metabolic response to changing extracellular levels of inorganic phosphate (Pi). Methods: All N. crassa strains were maintained on Vogel’s minimal medium, pH 5.8, at 30°C. Conidia from each strain were germinated for 5 h at 30°C in an orbital shaker (200 rpm), in low-Pi (10µM) and high-Pi (10mM) media. Total RNA was isolated from both strains and a total of 4 cDNA libraries were sequenced, with their respective biological triplicates corresponding to the paired libraries, using an Illumina HiSeq2000 sequencer, to generate 100 bp paired-end reads. FastQC software was used to visualize the library quality before and after trimming. For quality and sequence filtering, a Phred score lower than 20 was employed to remove sequencing bases from the read ends. Filtered reads were mapped onto the N. crassa genome using Bowtie2 software. The reads count values were obtained and used to calculate the expression variation of the transcripts from different conditions, considering the statistical significance of the differential gene expression. qRT–PCR validation was performed using SYBR Green assays. Results: extracellular Pi availability influenced the expression of genes involved in several biological functions. The main affected gene groups were those associated with integral components of the membrane, such as transport, regulation, and cell signalling pathways, as well as genes involved with the nucleolus and protein synthesis. The absence of mus-52 affected global gene transcription in all conditions tested, highlighting the expression of some specific gene groups, such as transcription factors, kinase proteins, circadian clock-related genes, oxi-reduction balance, phosphate pathways, and general metabolism. Conclusions: The consequences of N. crassa mus-52 disruption to the cell may be deeper than the obvious phenotypic aspect. It may affect canonical and non-canonical pathways, leading to alternative adaptive processes, altering the perception and response to the environmental changes.
Project description:Whole-genome single-base resolution methylcytosine map reveals profound changes that occur after Lsh deletion during embryonic development in primary WT and Lsh-/- MEFs. Lsh deletion leads to widespread decreases of CG methylation level at uniquely mapped genomic regions compared to wild type, including TSSs at protein-coding genes, and non-coding RNA genes. MethylC-Seq from Mus musculus primary MEFs.
Project description:Cryptochromes were identified in plants and animals where they function as either photoreceptors or circadian clock components. In the filamentous fungus Neurospora, the biological function of cryptochrome has not yet been explored. Here, we demonstrate that Neurospora crassa cryptochrome (Nc cry) is a DASH-type of cryptochrome, capable of binding FAD and MTHF, whose transcript and protein levels are both strongly induced by blue light in a wc-1 dependent manner. Although the Nc cry transcript is circadian-regulated and antiphasic to frq, knockout strains of Nc cry appears to have a normal clock phenotype. Whole genome microarray and RT-QPCR analysis confirm that Nc cry is not involved in the signal transduction of either early or late light responses and seems to have no transcriptional regulatory activity under our laboratory conditions. Our study concludes that the only cryptochrome in Neurospora crassa is dispensable for the well-characterized blue light sensing cascade and is not part of the circadian clock system. Keywords: light response