Project description:Purpose: quantitavive RT-PCR and ChIP analyses suggested that the MYC-Associated factor X, MAX, and the essential circadian regulator, BMAL1, might be recruited on the same E-box containing regulatory regions within the promoters of clock target genes. To explore this possibility, we performed ChIP-seq experiments in human cancer MDA-MB-231 cells. Methods: Chromatin samples from human cancer MDA-MB-231 cells were immunoprecipitated with specific antibodies against BMAL1 and MAX proteins. Immunoprecipitated DNA was sequenced using Illumina HiSeq 2000 sequencer. Results: ChIP-seq analysis revealed a large number of genomic regions bound by MAX (around 13000 peaks), while BMAL1 binding was limited to about 800 regions. BMAl1 and MAX bound regions comprised both promoters and distal sites. Coherently with the circadian role of BMAL1 and its preference for E-box-containing sites, ontological annotation of BMAL1 bound regions showed a significant enrichment for circadian regulated genes and E-box motifs. The 85% of the BMAL bound sites overlapped with MAX bound regions. MAX enrichment was higher on the genomic regions co-bound by BMAL1 compared with MAX binding loci sites in which BMAL1 was not present, thus indicating that MAX/BMAL1 sites are bound by MAX with high affinity. Strikingly, MAX enrichment was observed on all E-box-containing promoters of the clock core genes.
Project description:Basic helix-loop-helix (bHLH) transcription factors (TF) recognize E-boxes (CANNTG) and include over 100 members. Here we investigated how chromatinised E-boxes are engaged by two structurally diverse bHLH family members; the proto-oncogene MYC-MAX and the circadian TF, CLOCK-BMAL1. Both bind E-boxes preferentially near the nucleosomal entry/exit sites. Structural studies with artificial or endogenous nucleosome sequences illustrate that MYC-MAX/CLOCK-BMAL1 trigger DNA release from histones to gain access. The CLOCK-BMAL1 PAS dimerization domains engage the histone-octamer disc atop the H2A/H2B acidic patch, an interaction critical for circadian cycling. Binding of tandem E-boxes at endogenous DNA sequences is similarly achieved through direct interactions between two CLOCK-BMAL1 protomers and histones. At internal E-boxes, the MYC-MAX leucine zipper can also interact with histones H2B/H3, and its binding is indirectly enhanced by OCT4 elsewhere on the nucleosome. The nucleosomal E-box position and the type of bHLH dimerisation domain jointly determine the histone contact, the affinity, and the degree of competition/cooperativity with other nucleosome-bound factors.
Project description:In this project, we used affinity purification and label-free quantitative proteomics to identify BMAL1-interacting proteinsin HEK293T cells.
Project description:Purpose: Quantitative RT-PCR and ChIP analyses identified MAX as a transcriptional repressor of circadian BMAL1 target genes. The goal of this study is to compare the transcriptional effect of a knockdown of either MAX and BMAL1 in a human cell line (MDA-MB-231) Methods: Polyadenylated mRNA profiles of human breast cancer MDA-MB-231 cells with knocked down MAX or BMAL1 were generated by deep sequencing, in triplicate, using Illumina HiSeq 2000 sequencer. Cells transfected with a non-targeting siRNA sequence were used as a control. RNA sequencing counts were used to determine differentially expressed genes with DeSeq2 package included in the Galaxy web platform (usergalaxy.org). Differentially expressed genes (DEGs) were defined adopting an adjust P < 0.001 as a statistical cut-off value. Results: Transcript assembly and quantification of RNA-sequencing reads identified 4863 and 4247 differentially expressed genes (DEGs) upon knockdown of BMAL1 or MAX, respectively. The comparison of the two set of genes revealed that 2391 of siBMAL1 DEGs (almost 50%) were also differentially expressed in MAX-silenced cells. Heat map and clustering analysis of this sub-set of genes revealed that more than 90% (2241 out of 2391) were coherently altered in both conditions (i.e. their expression was altered in the same direction). Consistent with our quantitative RT-PCR experiments, genes belonging to the circadian rhythm signalling were altered by both MAX and BMAL1 silencing. Conclusion: This study indicate that MAX is a part of the molecular clock transcriptional network.
Project description:The product of the Bmal1 locus is an essential component of the circadian clock that plays important roles in various aspects of reproductive biology,and when disrupted results in infertility. In an effort to establish the identity of the tissue specific clock that is responsible for this infertility, we used the steroidogenic factor-1 (Sf1) promoter to drive Cre-mediated recombination and genetically delete Bmal1 within cells of the reproductive axis. We show that Bmal1 within the reproductive axis of females is essential for normal fertility through its role in maintaining implantation, but is not required for normal estrous cycling. At the root of this biology appears to be a defect in the ovaries, including regulation of ovarian lipid biosynthetic or metabolic processes and their roles in maintaining progesterone synthesis. This conclusion is based upon three observations. First, that deletion of Bmal1 within the reproductive axis reducesleads to affected transcripts in steroidogenic pathways for the LH receptor , and lowers progesterone levels. Second, that progesterone supplementation of these conditional mutants rescues implantation. Third, transplantation of wild type ovaries into Bmal1 reproductive axis mutants rescues fertility. Our study demonstrates the significance of ovarian Bmal1 as an overriding influence in experimental models of infertility. A time series was performed in time-mated C57Bl/6J mice to identiy oscillating transcripts. During the peak and trough of the majority of transcripts (ZT0 and ZT12) samples from Bmal1fx/fx Sf1Cre mice and control litermates as well and global Bmal1 nulls were also analyzed. The tissue types (ovary, pituitary) are not comparable.
Project description:TMT analysis of proteomic changes in the gastrocnemius skeletal muscles of WT and Bmal1-KO mice, and Bmal1-KO mice rescued with AAV-mediated muscle-specific expression of Bmal1.
Project description:The product of the Bmal1 locus is an essential component of the circadian clock that plays important roles in various aspects of reproductive biology, and its disruption results in infertility. In an effort to identify the identity of the tissue specific clock that is responsible for this infertility, we used the steroidogenic factor-1 (Sf1) promoter to drive Cre-mediated recombination and genetically delete Bmal1 within cells of the reproductive axis. We show that Bmal1 within the reproductive axis of females is essential for normal fertility through its role in maintaining implantation, but is not required for normal estrous cycling. At the root of this biology appears to be a defect in the regulation of ovarian steroidogenic acute regulator (StAR) and its role in maintaining progesterone synthesis. This conclusion is based upon three observations. First, that deletion of Bmal1 within the reproductive axis leads to lower levels of StAR mRNA, and lower progesterone levels. Second, that progesterone supplementation of these conditional mutants rescues implantation. Third, transplantation of wild type ovaries into Bmal1 reproductive axis mutants results in 100% fertility. Our study suggests that ovarian Bmal1 is an essential peripheral clock governing implantation and fertility in female mice. Ten week old female Bmal1fxfx mice positive or negative for Cre-recombinase driven by the sf-1 promoter, housed in 12 hour light:12 dark, ad lib feeding and drinking conditions were sacrificed at ZT12 on 3.5dpc (3.5 days post copulation). For each array analysis, a pool of 3 RNA samples from 3 individual Bmal1fx/fxCresf-1 ovaries labeled with cy3 were co-hybridized with a pool of 3 RNA samples from Bmal1fx/fx ovaries labeled with cy5, according to Agilent protocols.
Project description:The Myc-Max heterodimer is a DNA binding protein that regulates expression of a large number of genes. Genome occupancy of Myc-Max is thought to be driven by E-boxes (CACGTG or variants) to which the heterodimer binds in vitro. By analyzing ChIP-Seq datasets, we demonstrated that the positions occupied by Myc-Max across the human genome correlate with the RNA polymerase II (Pol II) transcription machinery better than with E-boxes. Metagene analyses showed that in promoter regions, Myc was uniformly positioned about 100 bp upstream of essentially all promoter proximal paused polymerases with Max about 10 bp upstream of Myc. We re-evaluated the DNA binding properties of full length Myc-Max proteins using electrophoretic mobility shift assays (EMSA) and protein-binding microarrays (PBM). EMSA results demonstrated Myc-Max heterodimers have high affinity for both E-box containing and non-specific DNA. Quantification of the relative affinities of Myc-Max for all possible 8- mers using PBM assays showed that sequences surrounding core 6-mers significantly affect binding. Comparing to the in vitro sequence preferences, Myc-Max genomic occupancy measured by ChIP-Seq was largely, although not completely, independent of sequence specificity. Our results suggest that the transcription machinery and associated promoter accessibility play an important role in genomic occupancy of Myc.
Project description:To define regulation of tissue proteomes by Bmal1, daily feeding rhythm, and the interaction, we employed Bmal1-stopFL mice, which do not express the main transcriptional activator of the molecular clock, Bmal1, except in cre recombinase-expressing cells1,2 (Figure 1A). Bmal1-stopFL mice lacking cre (Bmal1 knockout, KO) are analogous to Bmal1-null mice and display severely impaired behavioral and molecular rhythms1-3. Hepatocyte-specific Alfp-cre and skeletal muscle-specific Hsa-cre genes were introduced to generate a single line wherein both hepatocyte and skeletal muscle Bmal1 were reconstituted (Liver+Muscle-RE), i.e., rescued (Smith, Koronowski et al. 2023). This approach had the benefit of analyzing liver and muscle from the same mice but comes with the qualification that the abundance of some proteins may be influenced by Bmal1 function in the other tissue, or by a synergistic effect of Bmal1 in both tissues, rather than through rescue of local Bmal1 function alone. Proteomic anlaysis was performed in liver and skeletal muscle.
Project description:The product of the Bmal1 locus is an essential component of the circadian clock that plays important roles in various aspects of reproductive biology, and its disruption results in infertility. In an effort to identify the identity of the tissue specific clock that is responsible for this infertility, we used the steroidogenic factor-1 (Sf1) promoter to drive Cre-mediated recombination and genetically delete Bmal1 within cells of the reproductive axis. We show that Bmal1 within the reproductive axis of females is essential for normal fertility through its role in maintaining implantation, but is not required for normal estrous cycling. At the root of this biology appears to be a defect in the regulation of ovarian steroidogenic acute regulator (StAR) and its role in maintaining progesterone synthesis. This conclusion is based upon three observations. First, that deletion of Bmal1 within the reproductive axis leads to lower levels of StAR mRNA, and lower progesterone levels. Second, that progesterone supplementation of these conditional mutants rescues implantation. Third, transplantation of wild type ovaries into Bmal1 reproductive axis mutants results in 100% fertility. Our study suggests that ovarian Bmal1 is an essential peripheral clock governing implantation and fertility in female mice.