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DNA specificity determinants associate with distinct transcription factor functions

ABSTRACT: To elucidate how genomic sequences build transcriptional control networks we need to understand the connection between DNA sequence and transcription factor binding and function. Binding predictions based solely on consensus predictions are limited because a single factor can use degenerate sequence motifs and related transcription factors often prefer identical sequences. The ETS family transcription factor, ETS1, exemplifies these challenges. Unexpected, redundant occupancy of ETS1 and other ETS proteins is observed at promoters of housekeeping genes in T cells due to common sequence preferences and the presence of strong consensus motifs. However, ETS1 exhibits a specific function in T cell activation, thus unique transcriptional targets are predicted. To uncover the sequence motifs that mediate specific functions of ETS1, chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq) identified both promoter and enhancer binding events in Jurkat T cells. A comparison with DNase I sensitivity both validated the dataset and improved accuracy. Redundant occupancy of ETS1 with the ETS protein GABPA occurred primarily in promoters of housekeeping genes, whereas ETS1 specific occupancy occurred in the enhancers of T-cell specific genes. Two routes to ETS1 specificity were identified: an intrinsic preference of ETS1 for a variant of the ETS family consensus sequence and the presence of a composite sequence that can support cooperative binding with a RUNX transcription factor. Genome-wide occupancy of RUNX factors corroborated the importance of this partnership. Furthermore, genome-wide occupancy of co-activator CBP indicated tight co-localization with ETS1 at specific enhancers, but not redundant promoters. The distinct sequences associated with redundant versus specific ETS1 occupancy were predictive of promoter or enhancer location and the ontology of nearby genes. These findings demonstrate that diversity of binding motifs may enable variable transcription factor function at different genomic sites.

ORGANISM(S): Homo sapiens

PROVIDER: GSE17954 | GEO | 2009/12/18

SECONDARY ACCESSION(S): PRJNA119913

REPOSITORIES: GEO

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Project description:To elucidate how genomic sequences build transcriptional control networks we need to understand the connection between DNA sequence and transcription factor binding and function. Binding predictions based solely on consensus predictions are limited because a single factor can use degenerate sequence motifs and related transcription factors often prefer identical sequences. The ETS family transcription factor, ETS1, exemplifies these challenges. Unexpected, redundant occupancy of ETS1 and other ETS proteins is observed at promoters of housekeeping genes in T cells due to common sequence preferences and the presence of strong consensus motifs. However, ETS1 exhibits a specific function in T cell activation, thus unique transcriptional targets are predicted. To uncover the sequence motifs that mediate specific functions of ETS1, chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq) identified both promoter and enhancer binding events in Jurkat T cells. A comparison with DNase I sensitivity both validated the dataset and improved accuracy. Redundant occupancy of ETS1 with the ETS protein GABPA occurred primarily in promoters of housekeeping genes, whereas ETS1 specific occupancy occurred in the enhancers of T-cell specific genes. Two routes to ETS1 specificity were identified: an intrinsic preference of ETS1 for a variant of the ETS family consensus sequence and the presence of a composite sequence that can support cooperative binding with a RUNX transcription factor. Genome-wide occupancy of RUNX factors corroborated the importance of this partnership. Furthermore, genome-wide occupancy of co-activator CBP indicated tight co-localization with ETS1 at specific enhancers, but not redundant promoters. The distinct sequences associated with redundant versus specific ETS1 occupancy were predictive of promoter or enhancer location and the ontology of nearby genes. These findings demonstrate that diversity of binding motifs may enable variable transcription factor function at different genomic sites. Each ChIP sample was pooled from three independent immunoprecipitation experiments

Project description:Runx1 and Runx3 function redundantly in early T-development, and together drive T-lineage developmental progression by regulating distinct sets of genes in different stages. Context-specific Runx target genes are particularly enriched near Runx binding sites that dynamically shift from pre-T-commitment stages (Phase 1) to post-T-commitment stages (Phase 2). As total Runx activities (Runx1+Runx3) are maintained stably throughout early T-development stages, yet Runx factors physically interact with multiple collaborators, we hypothesized that different Runx-collaborating transcription factors compete to recruit a limited pool of Runx transcription factors. To test whether increasing Runx availability can alter Runx DNA-binding site choices, Runx1 overexpression vectors were introduced to two different systems. First, we increased Runx1 expression in a DN3-like cell line (representing a post-commitment, Phase 2 stage) in the presence or absence of exogenous Phase 1 co-factor, PU.1. Second, we increased Runx1 expression in Phase 1 primary cells which naturally express PU.1 and other Phase 1 collaborators. Then, Runx1 binding behaviors were measured using ChIP-seq or CUT&RUN (C&R). A modest increase of Runx1 levels (about 2-3 fold increase) substantially increased the number of Runx binding sites seen and the intensity of occupancy in both systems. When Runx expression was at physiological levels, PU.1 dominated Runx1 site choice before T commitment by recruiting Runx1 to PU.1 sites. The Phase 2 cell line system showed that it did this while depleting Runx1 from alternative high quality Runx motif sites. However, when Runx1 was overexpressed, Runx1 was still recruited to PU.1 sites, but this recruitment did not evacuate Runx1 occupancy from default preferred sites. Notably, Runx1 overexpression in primary Phase 1 cells caused precocious occupancy of post-commitment, Phase 2-specific sites. We found that these are often co-occupied with TCF1, E2A, and HEB, but have minimal co-binding with PU.1. In addition, Runx1 overexpression resulted in new binding sites that were not normally observed in pro-T cells, which are mostly sequestered by closed chromatin normally although they harbor more numerous Runx motifs. Thus, these data suggest that Runx DNA binding site choices are sensitive to Runx concentration and co-factors during early T-development.

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DNA specificity determinants associate with distinct transcription factor functions

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