Characterization of tissue-specific BMAL1 cistromes reveals new roles for enhancer-enhancer interactions in regulating rhythmic transcription [ChIA-PET]
Ontology highlight
ABSTRACT: The mammalian circadian clock relies on the transcription factor CLOCK:BMAL1 to coordinate the rhythmic expression of thousands of genes and enable biological functions to anticipate the daily environmental variations. Consistent with the wide range of biological functions under clock control, rhythmic gene expression is tissue-specific, and this even if the clockwork mechanism is identical in every cell. Here we show that BMAL1 DNA binding is largely tissue-specific, through mechanisms involving differences in chromatin accessibility between tissues as well as co-binding of tissue-specific transcription factors. Our results also indicate that the ability of BMAL1 to drive tissue-specific rhythmic transcription not only relies on the activity of BMAL1 cis-regulatory elements (CREs), but also on the activity of neighboring CREs. Characterization of the physical interactions between BMAL1 CREs and other CREs by RNA Polymerase II ChIA-PET in the mouse liver reveals that most interactions are stable over the course of the day, and suggests that BMAL1-mediated rhythmic transcription relies on its ability to regulate the transcriptional activity of other CREs. Our data therefore suggest that much of BMAL1 target gene transcription depends on BMAL1 capacity at rhythmically regulating a network of enhancers.
Project description:The mammalian circadian clock relies on the transcription factor CLOCK:BMAL1 to coordinate the rhythmic expression of thousands of genes and enable biological functions to anticipate the daily environmental variations. Consistent with the wide range of biological functions under clock control, rhythmic gene expression is tissue-specific, and this even if the clockwork mechanism is identical in every cell. Here we show that BMAL1 DNA binding is largely tissue-specific, through mechanisms involving differences in chromatin accessibility between tissues as well as co-binding of tissue-specific transcription factors. Our results also indicate that the ability of BMAL1 to drive tissue-specific rhythmic transcription not only relies on the activity of BMAL1 cis-regulatory elements (CREs), but also on the activity of neighboring CREs. Characterization of the physical interactions between BMAL1 CREs and other CREs by RNA Polymerase II ChIA-PET in the mouse liver reveals that most interactions are stable over the course of the day, and suggests that BMAL1-mediated rhythmic transcription relies on its ability to regulate the transcriptional activity of other CREs. Our data therefore suggest that much of BMAL1 target gene transcription depends on BMAL1 capacity at rhythmically regulating a network of enhancers.
Project description:The mammalian circadian clock relies on the master genes CLOCK (CLK) and BMAL1 and drives rhythmic gene expression to regulate biological functions under circadian control. We recently uncovered a surprising disconnect between the rhythmic binding of CLK:BMAL1 on DNA and the transcription of its target genes, suggesting that they are regulated by as yet uncharacterized mechanisms. Here we show that rhythmic CLK:BMAL1 DNA binding promotes rhythmic chromatin opening. The underlying mechanisms include CLK:BMAL1 binding to nucleosomes and rhythmic chromatin modifications, including the incorporation of the histone variant H2A.Z. This rhythmic chromatin remodeling mediates the rhythmic binding of other transcription factors adjacent to CLK:BMAL1, suggesting that the activity and the tissue-specific expression of these other transcription factors contribute to the genome-wide CLK:BMAL1 heterogeneous transcriptional output. These data therefore indicate that the clock regulation of transcription relies on the rhythmic regulation of chromatin accessibility and suggest that the concept of pioneer function extends to acute gene regulation, well beyond the current confines of developmental/cell specification. H2A.Z ChIP-Seq signal in the mouse liver over 6 time points of the 24h light:dark cycle, in wild-type and Bmal1-/- mice. Libraries containing a mononucleosome insert were sequenced using Ilumina HiSeq2000.
Project description:The mammalian circadian clock relies on the master genes CLOCK (CLK) and BMAL1 and drives rhythmic gene expression to regulate biological functions under circadian control. We recently uncovered a surprising disconnect between the rhythmic binding of CLK:BMAL1 on DNA and the transcription of its target genes, suggesting that they are regulated by as yet uncharacterized mechanisms. Here we show that rhythmic CLK:BMAL1 DNA binding promotes rhythmic chromatin opening. The underlying mechanisms include CLK:BMAL1 binding to nucleosomes and rhythmic chromatin modifications, including the incorporation of the histone variant H2A.Z. This rhythmic chromatin remodeling mediates the rhythmic binding of other transcription factors adjacent to CLK:BMAL1, suggesting that the activity and the tissue-specific expression of these other transcription factors contribute to the genome-wide CLK:BMAL1 heterogeneous transcriptional output. These data therefore indicate that the clock regulation of transcription relies on the rhythmic regulation of chromatin accessibility and suggest that the concept of pioneer function extends to acute gene regulation, well beyond the current confines of developmental/cell specification. Mouse liver nucleosome profile assayed by MNase-Seq over 6 time points of the 24h light:dark cycle (4 wild-type and 4 Bmal1-/- mice per time point). Illumina libraries containing a mononucleosome insert were sequenced using Ilumina HiSeq2000.
Project description:The mammalian circadian clock relies on the master genes CLOCK (CLK) and BMAL1 and drives rhythmic gene expression to regulate biological functions under circadian control. We recently uncovered a surprising disconnect between the rhythmic binding of CLK:BMAL1 on DNA and the transcription of its target genes, suggesting that they are regulated by as yet uncharacterized mechanisms. Here we show that rhythmic CLK:BMAL1 DNA binding promotes rhythmic chromatin opening. The underlying mechanisms include CLK:BMAL1 binding to nucleosomes and rhythmic chromatin modifications, including the incorporation of the histone variant H2A.Z. This rhythmic chromatin remodeling mediates the rhythmic binding of other transcription factors adjacent to CLK:BMAL1, suggesting that the activity and the tissue-specific expression of these other transcription factors contribute to the genome-wide CLK:BMAL1 heterogeneous transcriptional output. These data therefore indicate that the clock regulation of transcription relies on the rhythmic regulation of chromatin accessibility and suggest that the concept of pioneer function extends to acute gene regulation, well beyond the current confines of developmental/cell specification. Mouse liver CLK ChIP-Seq signal on Mnase-digested or sonicated chromatin, at 2 different time point (ZT22 and ZT06) from the same mice. Libraries were sequenced using Ilumina HiSeq2000. For Mnase-digested chromatin, libraries contained a mononucleosome insert (e.g., ~147bp), whereas the insert was ~150-300bp for sonicated chromatin.
Project description:The mammalian circadian clock relies on the master genes CLOCK (CLK) and BMAL1 and drives rhythmic gene expression to regulate biological functions under circadian control. We recently uncovered a surprising disconnect between the rhythmic binding of CLK:BMAL1 on DNA and the transcription of its target genes, suggesting that they are regulated by as yet uncharacterized mechanisms. Here we show that rhythmic CLK:BMAL1 DNA binding promotes rhythmic chromatin opening. The underlying mechanisms include CLK:BMAL1 binding to nucleosomes and rhythmic chromatin modifications, including the incorporation of the histone variant H2A.Z. This rhythmic chromatin remodeling mediates the rhythmic binding of other transcription factors adjacent to CLK:BMAL1, suggesting that the activity and the tissue-specific expression of these other transcription factors contribute to the genome-wide CLK:BMAL1 heterogeneous transcriptional output. These data therefore indicate that the clock regulation of transcription relies on the rhythmic regulation of chromatin accessibility and suggest that the concept of pioneer function extends to acute gene regulation, well beyond the current confines of developmental/cell specification.
Project description:The mammalian circadian clock relies on the master genes CLOCK (CLK) and BMAL1 and drives rhythmic gene expression to regulate biological functions under circadian control. We recently uncovered a surprising disconnect between the rhythmic binding of CLK:BMAL1 on DNA and the transcription of its target genes, suggesting that they are regulated by as yet uncharacterized mechanisms. Here we show that rhythmic CLK:BMAL1 DNA binding promotes rhythmic chromatin opening. The underlying mechanisms include CLK:BMAL1 binding to nucleosomes and rhythmic chromatin modifications, including the incorporation of the histone variant H2A.Z. This rhythmic chromatin remodeling mediates the rhythmic binding of other transcription factors adjacent to CLK:BMAL1, suggesting that the activity and the tissue-specific expression of these other transcription factors contribute to the genome-wide CLK:BMAL1 heterogeneous transcriptional output. These data therefore indicate that the clock regulation of transcription relies on the rhythmic regulation of chromatin accessibility and suggest that the concept of pioneer function extends to acute gene regulation, well beyond the current confines of developmental/cell specification.
Project description:The mammalian circadian clock relies on the master genes CLOCK (CLK) and BMAL1 and drives rhythmic gene expression to regulate biological functions under circadian control. We recently uncovered a surprising disconnect between the rhythmic binding of CLK:BMAL1 on DNA and the transcription of its target genes, suggesting that they are regulated by as yet uncharacterized mechanisms. Here we show that rhythmic CLK:BMAL1 DNA binding promotes rhythmic chromatin opening. The underlying mechanisms include CLK:BMAL1 binding to nucleosomes and rhythmic chromatin modifications, including the incorporation of the histone variant H2A.Z. This rhythmic chromatin remodeling mediates the rhythmic binding of other transcription factors adjacent to CLK:BMAL1, suggesting that the activity and the tissue-specific expression of these other transcription factors contribute to the genome-wide CLK:BMAL1 heterogeneous transcriptional output. These data therefore indicate that the clock regulation of transcription relies on the rhythmic regulation of chromatin accessibility and suggest that the concept of pioneer function extends to acute gene regulation, well beyond the current confines of developmental/cell specification.
Project description:Over the past decade, genome-wide assays have underscored the broad sweep of circadian gene expression. A substantial fraction of the transcriptome undergoes oscillations in many organisms and tissues, which governs the many biochemical, physiological and behavioral functions under circadian control. Based predominantly on the transcription feedback loops important for core circadian timekeeping, it is commonly assumed that this widespread mRNA cycling reflects circadian transcriptional cycling. To address this issue, we directly measured dynamic changes in mouse liver transcription using Nascent-Seq. Many genes are rhythmically transcribed over the 24h day, which include precursors of several non-coding RNAs as well as the expected set of core clock genes. Surprisingly however, nascent RNA rhythms overlap poorly with mRNA abundance rhythms assayed by RNA-seq. This is because most mouse liver genes with rhythmic mRNA expression manifest poor transcriptional rhythms, indicating a prominent role of post-transcriptional regulation in setting mRNA cycling amplitude. To gain further insight into circadian transcriptional regulation, we also characterized the rhythmic transcription of liver genes targeted by the transcription factors CLOCK and BMAL1; they directly target other core clock genes and sit at the top of the molecular circadian clock hierarchy in mammals. CLK:BMAL1 rhythmically bind at the same discrete phase of the circadian cycle to all target genes, which not surprisingly have a much higher percentage of rhythmic transcription than the genome as a whole. However, there is a surprisingly heterogeneous set of cycling transcription phases of direct target genes, which even include core clock genes. This indicates a disconnect between rhythmic DNA binding and the peak of transcription, which is likely due to other transcription factors that collaborate with CLK:BMAL1. In summary, the application of Nascent-Seq to a mammalian tissue provides surprising insights into the rhythmic control of gene expression and should have broad applications beyond the analysis of circadian rhythms. CLK and BMAL1 DNA binding profile in the mouse liver at ZT8, sequenced along an Input sample using GAII (ChIP-Seq) Supplementary file ChIPSeq_Mouse_Liver_Processed_data_Table1.txt represents annotated CLK and BMAL1 peaks.
Project description:Diurnal oscillations of gene expression are a hallmark of rhythmic physiology across most living organisms. Such oscillations are controlled by the interplay between the circadian clock and feeding rhythms. While rhythmic mRNA accumulation has been extensively studied, comparatively less is known about their transcription and translation. Here, we quantified simultaneously temporal transcription, accumulation, and translation of mouse liver mRNAs under physiological light-dark conditions and ad libitum or night-restricted feeding in wild-type and Bmal1 deficient animals. We found that rhythmic transcription predominantly drives rhythmic mRNA accumulation and translation for a majority of genes. Comparison of wild-type and Bmal1 KO mice shows that circadian clock and feeding rhythms have broad impact on rhythmic genes expression, Bmal1 deletion having surprisingly more impact at the post-transcriptional level. Translation efficiency is differentially regulated during the diurnal cycle for genes with 5â-TOP sequences and for genes involved in mitochondrial activity and harboring a TISU motif. The increased translation efficiency of 5â-TOP and TISU genes is mainly driven by feeding rhythms but Bmal1 deletion impacts also amplitude and phase of translation, including TISU genes. Together this study emphasizes the complex interconnections between circadian and feeding rhythms at several steps ultimately determining rhythmic gene expression and translation. RNA-Seq from total RNA of mouse liver during the dirunal cycle. Time-series mRNA profiles of wild type (WT) and Bmal -/- mice under ad libitum and night restriced feeding regimen were generated by deep sequencing.
Project description:Over the past decade, genome-wide assays have underscored the broad sweep of circadian gene expression. A substantial fraction of the transcriptome undergoes oscillations in many organisms and tissues, which governs the many biochemical, physiological and behavioral functions under circadian control. Based predominantly on the transcription feedback loops important for core circadian timekeeping, it is commonly assumed that this widespread mRNA cycling reflects circadian transcriptional cycling. To address this issue, we directly measured dynamic changes in mouse liver transcription using Nascent-Seq. Many genes are rhythmically transcribed over the 24h day, which include precursors of several non-coding RNAs as well as the expected set of core clock genes. Surprisingly however, nascent RNA rhythms overlap poorly with mRNA abundance rhythms assayed by RNA-seq. This is because most mouse liver genes with rhythmic mRNA expression manifest poor transcriptional rhythms, indicating a prominent role of post-transcriptional regulation in setting mRNA cycling amplitude. To gain further insight into circadian transcriptional regulation, we also characterized the rhythmic transcription of liver genes targeted by the transcription factors CLOCK and BMAL1; they directly target other core clock genes and sit at the top of the molecular circadian clock hierarchy in mammals. CLK:BMAL1 rhythmically bind at the same discrete phase of the circadian cycle to all target genes, which not surprisingly have a much higher percentage of rhythmic transcription than the genome as a whole. However, there is a surprisingly heterogeneous set of cycling transcription phases of direct target genes, which even include core clock genes. This indicates a disconnect between rhythmic DNA binding and the peak of transcription, which is likely due to other transcription factors that collaborate with CLK:BMAL1. In summary, the application of Nascent-Seq to a mammalian tissue provides surprising insights into the rhythmic control of gene expression and should have broad applications beyond the analysis of circadian rhythms. Mouse liver nascent RNA profile over 6 time points of the 24h light:dark cycle, in duplicate, sequenced using Ilumina GAII (Nascent-Seq); Mouse liver mRNA profile over 6 time points of the 24h light:dark cycle, in duplicate, sequenced using Ilumina HiSeq2000 (RNA-Seq); CLK and BMAL1 DNA binding profile in the mouse liver at ZT8, sequenced along an Input sample using GAII (ChIP-Seq); Mouse liver strand-specific nascent RNA profile over 6 time points of the 24h light:dark cycle, in duplicate, sequenced using Ilumina HiSeq2000 (Strand-specific Nascent-Seq);