Project description:The chromatin remodeling complexes CHRAC and ACF combine the ATPase ISWI with the signature subunit ACF1. These enzymes catalyze well-studied nucleosome sliding reactions in vitro, but how their actions affect physiological gene expression is unclear. Here we explored the influence of Drosophila CHRAC/ACF on transcription by complementary gain- and loss-of-function approaches. Targeting ACF1 to multiple reporter genes inserted at many different genomic locations revealed a context-dependent inactivation of poorly transcribed reporters in repressive chromatin. Accordingly, single-embryo transcriptome analysis of a Acf knock-out allele showed that only lowly expressed genes are de-repressed in the absence of ACF1. Finally, the nucleosome arrays in Acf-deficient chromatin show loss of physiological regularity, particularly in transcriptionally inactive domains. Taken together our results highlight that ACF1-containing remodeling factors contribute to the establishment of an inactive ground state of the genome through chromatin organization.
Project description:The chromatin remodeling complexes CHRAC and ACF combine the ATPase ISWI with the signature subunit ACF1. These enzymes catalyze well-studied nucleosome sliding reactions in vitro, but how their actions affect physiological gene expression is unclear. Here we explored the influence of Drosophila CHRAC/ACF on transcription by complementary gain- and loss-of-function approaches. Targeting ACF1 to multiple reporter genes inserted at many different genomic locations revealed a context-dependent inactivation of poorly transcribed reporters in repressive chromatin. Accordingly, single-embryo transcriptome analysis of a Acf knock-out allele showed that only lowly expressed genes are de-repressed in the absence of ACF1. Finally, the nucleosome arrays in Acf-deficient chromatin show loss of physiological regularity, particularly in transcriptionally inactive domains. Taken together our results highlight that ACF1-containing remodeling factors contribute to the establishment of an inactive ground state of the genome through chromatin organization.
Project description:Despite depression being one of the most prevalent and debilitating disorders worldwide, it has been difficult to understand its pathophysiology and to develop more effective treatments. Maladaptive transcriptional regulation within limbic neural circuits, including reward processing regions such as the nucleus accumbens (NAc), in response to chronic stress is thought to be a major contributor to the development of the syndrome. Epigenetic events?in particular, histone writers and erasers?that alter chromatin structure to regulate programs of gene expression have increasingly been associated with depression-related behavioral abnormalities in animal models and in depressed humans examined postmortem. However, very little is known about the ATP-dependent chromatin remodelers that control nucleosome positioning and the packing state of chromatin. Here we show that the ACF complex, part of the ISWI family of chromatin remodelers, is persistently and selectively upregulated in the NAc of mice that are susceptible to chronic social stress, as well as in the NAc of depressed human. We further establish that ACF induction is both necessary and sufficient for susceptibility to stress-induced depressive-like behaviors. Using ChIP-seq, we demonstrate that altered ACF binding after chronic stress is strongly correlated with altered nucleosome positioning, in particular, around the transcriptional start sites of affected genes. These alterations in ACF binding and nucleosome repositioning are associated with repressed expression of a subset of genes in animals that are susceptible to chronic stress. Together, these findings establish that active ATP-dependent chromatin remodeling by the ACF complex is a key regulator in the repression of genes that mediate susceptibility to social stress, and provide novel candidate targets for improved therapeutics of depression and other stress-related disorders. c57bl/6 mice underwent chronic social defeat stress (CSDS), and social interaction test was used to separate animals into control, susceptible and resilient groups. Nucleus accumbens (NAc) tissue was collected 48 hours after the last defeat session, and then Acf1, SNF2H ChIP-seq or H3 MNase-seq were performed based on the control, susceptible, and resilient groups. Three sequencing replicates were performed on each group.
Project description:Pluripotency is established in E4.5 preimplantation epiblast. Embryonic stem cells (ESCs) represent the immortalization of pluripotency, however, they only partially resemble the gene expression signature of developmental ground-state. Induced PRAMEL7 expression, a protein highly expressed in the ICM but lowly expressed in ESCs, reprograms developmentally advanced ESC+serum into ground-state pluripotency by inducing a gene expression signature close to developmental ground-state. However, how PRAMEL7 reprograms gene expression remains elusive. Here we show that PRAMEL7 associates with Cullin2 (CUL2) and this interaction is required to establish ground-state gene expression. PRAMEL7 recruits CUL2 to chromatin and targets for proteasomal degradation regulators of repressive chromatin, including NuRD complex. PRAMEL7 antagonizes NuRD-mediated repression of genes implicated in pluripotency by decreasing NuRD stability and promoter association in a CUL2-dependent manner. Our data link proteasome degradation pathways to ground-state gene expression, offering insights to generate in vitro models to reproduce the in vivo ground-state pluripotency.
Project description:Chromosomes have an intrinsic tendency to segregate into compartments, forming long-distance contacts between loci of similar chromatin states. How genome compartmentalization is regulated remains elusive. Here, comparison of mouse ground-state embryonic stem cells (ESCs) characterized by open and active chromatin, and advanced serum ESCs with a more closed and repressed genome, reveals distinct regulation of their genome organization due to differential dependency on BAZ2A/TIP5, a component of the chromatin remodeling complex NoRC. On ESC chromatin, BAZ2A interacts with SNF2H, DNA topoisomerase 2A (TOP2A) and cohesin. BAZ2A associates with chromatin subdomains within the active A compartment, which intersect through long-range contacts. We found that ground-state chromatin selectively requires BAZ2A to limit the invasion of active domains into repressive compartments. BAZ2A depletion increases chromatin accessibility at B compartments. Furthermore, BAZ2A regulates H3K27me3 genome occupancy in a TOP2A-dependent manner. Finally, ground-state ESCs require BAZ2A for growth, differentiation, and correct expression of developmental genes. Our results uncover the propensity of open chromatin domains to invade repressive domains, which is counteracted by chromatin remodeling to establish genome partitioning and preserve cell identity.
Project description:We apply deep small-RNA sequencing technology for high-throughput profiling of microRNAs in ground state embryonic stem cells (ESCs). We provide global expression signatures of microRNAs in ESCs cultured under serum, 2i, and R2i conditions. We report that microRNAs are significantly differentially expressed when ESCs are cultured under different conditions, and that ground state pluripotency features a uniqure microRNA signature which is mainly encoded by microRNA-coding sequences within the developmentally important DLK1-Dio3 locus. Finally, we indicate that microRNA upregulated in ground state pluripotent cells (i.e. 2i/R2i) contribute to the maintenace of ground state pluripotency through stimulating self-renewal and inhibiting multi-lineague differentiation.