Project description:Transcription factors (TFs) direct developmental transitions by binding to target DNA sequences, influencing gene expression and establishing complex gene-regultory networks. To systematically determine the molecular components that enable or constrain TF activity, we investigated the genomic occupancy of FOXA2, GATA4 and OCT4 in several cell types. Despite their classification as pioneer factors, all three TFs exhibit cell-type-specific binding, even when supraphysiologically and ectopically expressed. However, FOXA2 and GATA4 can be distinguished by low enrichment at loci that are highly occupied by these factors in alternative cell types. We find that expression of additional cofactors increases enrichment at a subset of these sites. Finally, FOXA2 occupancy and changes to DNA accessibility can occur in G1-arrested cells, but subsequent loss of DNA methylation requires DNA replication.
Project description:Transcription factors (TFs) are the core drivers of gene regulatory networks that control developmental transitions and a complete understanding of how they access, alter and maintain specific gene expression patterns remains an important goal. To begin a systematic dissection of the molecular components that either enable or constrain TF activity, we investigated the genomic occupancy of two distinct TFs, the pioneer factor FOXA2 and the pluripotency-associated factor OCT4 (POU5F1), in both endogenous and ectopic settings. We find that, while stable binding of FOXA2 is highly cell type specific and similar to what is observed for most TFs including OCT4, pioneer activity can be distinguished by notable sampling of additional loci that are occupied in alternative lineages. In our ectopic system, FOXA2 binding can be selectively stabilized at previously sampled sites by co-expressing the lineage specific regulator GATA4. Alternatively, we observe minimal influence of chromatin state on discrete, stabilized binding choices for FOXA2 but a strong bias towards open chromatin for ectopic OCT4 targets. Finally, we demonstrate that FOXA2 binding and nucleosome remodeling at silent loci can occur when the cell cycle is halted in G1, but surprisingly subsequent changes in DNA methylation require DNA replication. Taken together, our results provide several new molecular insights that contribute to our basic understanding of gene regulation and pave the way for a more rational use of ectopic TFs for cellular reprogramming.
Project description:Transcription factors (TFs) are the core drivers of gene regulatory networks that control developmental transitions and a complete understanding of how they access, alter and maintain specific gene expression patterns remains an important goal. To begin a systematic dissection of the molecular components that either enable or constrain TF activity, we investigated the genomic occupancy of two distinct TFs, the pioneer factor FOXA2 and the pluripotency-associated factor OCT4 (POU5F1), in both endogenous and ectopic settings. We find that, while stable binding of FOXA2 is highly cell type specific and similar to what is observed for most TFs including OCT4, pioneer activity can be distinguished by notable sampling of additional loci that are occupied in alternative lineages. In our ectopic system, FOXA2 binding can be selectively stabilized at previously sampled sites by co-expressing the lineage specific regulator GATA4. Alternatively, we observe minimal influence of chromatin state on discrete, stabilized binding choices for FOXA2 but a strong bias towards open chromatin for ectopic OCT4 targets. Finally, we demonstrate that FOXA2 binding and nucleosome remodeling at silent loci can occur when the cell cycle is halted in G1, but surprisingly subsequent changes in DNA methylation require DNA replication. Taken together, our results provide several new molecular insights that contribute to our basic understanding of gene regulation and pave the way for a more rational use of ectopic TFs for cellular reprogramming.
Project description:Transcription factors (TFs) are the core drivers of gene regulatory networks that control developmental transitions and a complete understanding of how they access, alter and maintain specific gene expression patterns remains an important goal. To begin a systematic dissection of the molecular components that either enable or constrain TF activity, we investigated the genomic occupancy of two distinct TFs, the pioneer factor FOXA2 and the pluripotency-associated factor OCT4 (POU5F1), in both endogenous and ectopic settings. We find that, while stable binding of FOXA2 is highly cell type specific and similar to what is observed for most TFs including OCT4, pioneer activity can be distinguished by notable sampling of additional loci that are occupied in alternative lineages. In our ectopic system, FOXA2 binding can be selectively stabilized at previously sampled sites by co-expressing the lineage specific regulator GATA4. Alternatively, we observe minimal influence of chromatin state on discrete, stabilized binding choices for FOXA2 but a strong bias towards open chromatin for ectopic OCT4 targets. Finally, we demonstrate that FOXA2 binding and nucleosome remodeling at silent loci can occur when the cell cycle is halted in G1, but surprisingly subsequent changes in DNA methylation require DNA replication. Taken together, our results provide several new molecular insights that contribute to our basic understanding of gene regulation and pave the way for a more rational use of ectopic TFs for cellular reprogramming.
Project description:Transcription factors (TFs) are the core drivers of gene regulatory networks that control developmental transitions and a complete understanding of how they access, alter and maintain specific gene expression patterns remains an important goal. To begin a systematic dissection of the molecular components that either enable or constrain TF activity, we investigated the genomic occupancy of two distinct TFs, the pioneer factor FOXA2 and the pluripotency-associated factor OCT4 (POU5F1), in both endogenous and ectopic settings. We find that, while stable binding of FOXA2 is highly cell type specific and similar to what is observed for most TFs including OCT4, pioneer activity can be distinguished by notable sampling of additional loci that are occupied in alternative lineages. In our ectopic system, FOXA2 binding can be selectively stabilized at previously sampled sites by co-expressing the lineage specific regulator GATA4. Alternatively, we observe minimal influence of chromatin state on discrete, stabilized binding choices for FOXA2 but a strong bias towards open chromatin for ectopic OCT4 targets. Finally, we demonstrate that FOXA2 binding and nucleosome remodeling at silent loci can occur when the cell cycle is halted in G1, but surprisingly subsequent changes in DNA methylation require DNA replication. Taken together, our results provide several new molecular insights that contribute to our basic understanding of gene regulation and pave the way for a more rational use of ectopic TFs for cellular reprogramming.
Project description:Transcription factors (TFs) are the core drivers of gene regulatory networks that control developmental transitions and a complete understanding of how they access, alter and maintain specific gene expression patterns remains an important goal. To begin a systematic dissection of the molecular components that either enable or constrain TF activity, we investigated the genomic occupancy of two distinct TFs, the pioneer factor FOXA2 and the pluripotency-associated factor OCT4 (POU5F1), in both endogenous and ectopic settings. We find that, while stable binding of FOXA2 is highly cell type specific and similar to what is observed for most TFs including OCT4, pioneer activity can be distinguished by notable sampling of additional loci that are occupied in alternative lineages. In our ectopic system, FOXA2 binding can be selectively stabilized at previously sampled sites by co-expressing the lineage specific regulator GATA4. Alternatively, we observe minimal influence of chromatin state on discrete, stabilized binding choices for FOXA2 but a strong bias towards open chromatin for ectopic OCT4 targets. Finally, we demonstrate that FOXA2 binding and nucleosome remodeling at silent loci can occur when the cell cycle is halted in G1, but surprisingly subsequent changes in DNA methylation require DNA replication. Taken together, our results provide several new molecular insights that contribute to our basic understanding of gene regulation and pave the way for a more rational use of ectopic TFs for cellular reprogramming.
Project description:Transcription factors (TFs) are the core drivers of gene regulatory networks that control developmental transitions and a complete understanding of how they access, alter and maintain specific gene expression patterns remains an important goal. To begin a systematic dissection of the molecular components that either enable or constrain TF activity, we investigated the genomic occupancy of two distinct TFs, the pioneer factor FOXA2 and the pluripotency-associated factor OCT4 (POU5F1), in both endogenous and ectopic settings. We find that, while stable binding of FOXA2 is highly cell type specific and similar to what is observed for most TFs including OCT4, pioneer activity can be distinguished by notable sampling of additional loci that are occupied in alternative lineages. In our ectopic system, FOXA2 binding can be selectively stabilized at previously sampled sites by co-expressing the lineage specific regulator GATA4. Alternatively, we observe minimal influence of chromatin state on discrete, stabilized binding choices for FOXA2 but a strong bias towards open chromatin for ectopic OCT4 targets. Finally, we demonstrate that FOXA2 binding and nucleosome remodeling at silent loci can occur when the cell cycle is halted in G1, but surprisingly subsequent changes in DNA methylation require DNA replication. Taken together, our results provide several new molecular insights that contribute to our basic understanding of gene regulation and pave the way for a more rational use of ectopic TFs for cellular reprogramming.
Project description:Transcription factors (TFs) are the core drivers of gene regulatory networks that control developmental transitions and a complete understanding of how they access, alter and maintain specific gene expression patterns remains an important goal. To begin a systematic dissection of the molecular components that either enable or constrain TF activity, we investigated the genomic occupancy of two distinct TFs, the pioneer factor FOXA2 and the pluripotency-associated factor OCT4 (POU5F1), in both endogenous and ectopic settings. We find that, while stable binding of FOXA2 is highly cell type specific and similar to what is observed for most TFs including OCT4, pioneer activity can be distinguished by notable sampling of additional loci that are occupied in alternative lineages. In our ectopic system, FOXA2 binding can be selectively stabilized at previously sampled sites by co-expressing the lineage specific regulator GATA4. Alternatively, we observe minimal influence of chromatin state on discrete, stabilized binding choices for FOXA2 but a strong bias towards open chromatin for ectopic OCT4 targets. Finally, we demonstrate that FOXA2 binding and nucleosome remodeling at silent loci can occur when the cell cycle is halted in G1, but surprisingly subsequent changes in DNA methylation require DNA replication. Taken together, our results provide several new molecular insights that contribute to our basic understanding of gene regulation and pave the way for a more rational use of ectopic TFs for cellular reprogramming.