Project description:PU.1 is a prototype master transcription factor (TF) of hematopoietic cell differentiation with diverse roles in different lineages. Analysis of its genome-wide binding pattern across PU.1 expressing cell types revealed manifold cell type-specific binding patterns. They are not consistent with the epigenetic and chromatin constraints to PU.1 binding observed in vitro, suggesting that PU.1 requires auxiliary factors to access DNA in vivo. Using a model of transient mRNA expression we show that PU.1 induction leads to the extensive remodeling of chromatin, redistribution of partner transcription factors and rapid initiation of a myeloid gene expression program in heterologous cell types. By probing PU.1 mutants for defects in chromatin access and screening for PU.1 proximal proteins in vivo, we found that its N-terminal acidic domain was required for the recruitment of SWI/SNF remodeling complexes, de novo chromatin access and stable binding as well as the redistribution of partner TFs.
Project description:Master transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARγ is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARγ without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARγ binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARγ cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator. Microarray expression profiling was performed on 3T3-L1 adipocytes from two treatment groups: (1) adipocytes transduced with a control adenovirus expressing beta-galactosidase (LACZ-Ads) and (2) adipocytes transduced with an adenovirus expressing full-length murine PU.1 cDNA (PU.1-Ads). Each sample group consists of four biological replicates which are here defined as separate differentiations of mature 3T3-L1 adipocytes and adenoviral infections. Each replicate was hybridized to an individual array for a total of eight arrays.
Project description:"Master" transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARM-NM-3 is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARM-NM-3 without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARM-NM-3 binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARM-NM-3 cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator. ChIP-seq was performed on 3T3-L1 adipocytes from two treatment groups: (1) adipocytes transduced with a control adenovirus expressing beta-galactosidase (LACZ-Ads) and (2) adipocytes transduced with an adenovirus expressing full-length murine PU.1 cDNA (PU.1-Ads). Nuclear lysates from each group were used for PPARg ChIP. For PU.1-Ads, PU.1 ChIP was also performed. To generate chromatin for ChIP-seq, DNA from three immunoprecipitations per condition was pooled. This process was repreated from a second set of L1 adipocytes to generate two biological replicates for sequencing. Genomic input DNA was sequenced from the first biological replicate only.
Project description:PU.1 is a prototype master transcription factor (TF) of hematopoietic cell differentiation with diverse roles in different lineages. Analysis of its genome-wide binding pattern across PU.1 expressing cell types revealed manifold cell type-specific binding patterns. They are not consistent with the epigenetic and chromatin constraints to PU.1 binding observed in vitro, suggesting that PU.1 requires auxiliary factors to access DNA in vivo. Using a model of transient mRNA expression we show that PU.1 induction leads to the extensive remodeling of chromatin, redistribution of partner transcription factors, and rapid initiation of a myeloid gene expression program in heterologous cell types. By probing mutant PU.1 variants for defects in chromatin access and screening for PU.1 proximal proteins in vivo, we found that its N-terminal acidic domain was required for the recruitment of SWI/SNF remodeling complexes, de novo chromatin access and stable binding as well as the redistribution of partner TFs.
Project description:PU.1 is a prototype master transcription factor (TF) of hematopoietic cell differentiation with diverse roles in different lineages. Analysis of its genome-wide binding pattern across PU.1 expressing cell types revealed manifold cell type-specific binding patterns. They are not consistent with the epigenetic and chromatin constraints to PU.1 binding observed in vitro, suggesting that PU.1 requires auxiliary factors to access DNA in vivo. Using a model of transient mRNA expression we show that PU.1 induction leads to the extensive remodeling of chromatin, redistribution of partner transcription factors, and rapid initiation of a myeloid gene expression program in heterologous cell types. By probing mutant PU.1 variants for defects in chromatin access and screening for PU.1 proximal proteins in vivo, we found that its N-terminal acidic domain was required for the recruitment of SWI/SNF remodeling complexes, de novo chromatin access and stable binding as well as the redistribution of partner TFs.
Project description:PU.1 is a prototype master transcription factor (TF) of hematopoietic cell differentiation with diverse roles in different lineages. Analysis of its genome-wide binding pattern across PU.1 expressing cell types revealed manifold cell type-specific binding patterns. They are not consistent with the epigenetic and chromatin constraints to PU.1 binding observed in vitro, suggesting that PU.1 requires auxiliary factors to access DNA in vivo. Using a model of transient mRNA expression we show that PU.1 induction leads to the extensive remodeling of chromatin, redistribution of partner transcription factors, and rapid initiation of a myeloid gene expression program in heterologous cell types. By probing mutant PU.1 variants for defects in chromatin access and screening for PU.1 proximal proteins in vivo, we found that its N-terminal acidic domain was required for the recruitment of SWI/SNF remodeling complexes, de novo chromatin access and stable binding as well as the redistribution of partner TFs.
Project description:Master transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARγ is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARγ without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARγ binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARγ cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator.
Project description:PU.1 is a prototype master transcription factor (TF) of hematopoietic cell differentiation with diverse roles in different lineages. Analysis of its genome-wide binding pattern across PU.1 expressing cell types revealed manifold cell type-specific binding patterns. They are not consistent with the epigenetic and chromatin constraints to PU.1 binding observed in vitro, suggesting that PU.1 requires auxiliary factors to access DNA in vivo. Using a model of transient mRNA expression we show that PU.1 induction leads to the extensive remodeling of chromatin, redistribution of partner transcription factors, and rapid initiation of a myeloid gene expression program in heterologous cell types. By probing mutant PU.1 variants for defects in chromatin access and screening for PU.1 proximal proteins in vivo, we found that its N-terminal acidic domain was required for the recruitment of SWI/SNF remodeling complexes, de novo chromatin access and stable binding as well as the redistribution of partner TFs.
Project description:"Master" transcription factors are the gatekeepers of lineage identity. As such, they have been a major focus of efforts to manipulate cell fate for therapeutic purposes. The ETS transcription factor PU.1 has a potent ability to confer macrophage phenotypes on cells already committed to a different lineage, but how it overcomes the presence of other master regulators is not known. The nuclear receptor PPARγ is the master regulator of the adipose lineage, and its genomic binding pattern is well characterized in adipocytes. Here, we show that when expressed at macrophage levels in mature adipocytes, PU.1 bound a large fraction of its macrophage sites, where it induced chromatin opening and the expression of macrophage target genes. Strikingly, PU.1 markedly reduced the genomic binding of PPARγ without changing its abundance. PU.1 expression repressed genes with nearby adipocyte-specific PPARγ binding sites, while a common macrophage-adipocyte gene expression program was retained. Together, these data reveal unexpected lability within the adipocyte PPARγ cistrome and show that even in terminally differentiated cells, PU.1 can remodel the cistrome of another master regulator.