Mechanisms governing target search and binding dynamics of hypoxia-inducible factors
- University of California, Berkeley, United States
Abstract
Transcription factors (TFs) are classically attributed a modular construction, containing well-structured sequence specific DNA-binding domains (DBDs) paired with disordered activation domains (ADs) responsible for protein-protein interactions targeting cofactors or the core transcription initiation machinery. However, this simple division of labor model struggles to explain why TFs with identical DNA binding sequence specificity determined in vitro exhibit distinct binding profiles in vivo. The family of Hypoxia-Inducible Factors (HIFs) offer a stark example: aberrantly expressed in several cancer types, HIF-1α and HIF-2α subunit isoforms recognize the same DNA motif in vitro - the hypoxia response element (HRE) - but only share a subset of their target genes in vivo, while eliciting contrasting effects on cancer development and progression under certain circumstances. To probe the mechanisms mediating isoform-specific gene regulation, we used live cell single particle tracking (SPT) to investigate HIF nuclear dynamics and how they change upon genetic perturbation or drug treatment. We found that HIF-α subunits and their dimerization partner HIF-1β exhibit distinct diffusion and binding characteristics that are exquisitely sensitive to concentration and subunit stoichiometry. Using domain-swap variants, mutations, and a HIF-2α specific inhibitor, we found that although the DBD and dimerization domains are important, another main determinant of chromatin binding and diffusion behavior is the AD-containing intrinsically disordered region (IDR). Using Cut&Run and RNA-seq as orthogonal genomic approaches we also confirmed IDR-dependent binding and activation of a specific subset of HIF-target genes. These findings reveal a previously unappreciated role of IDRs in regulating the TF search and binding process that contribute to functional target site selectivity on chromatin.
Data availability
NGS data have been deposited in NCBI's GEO under accession number GSE207575.SPT raw data are accessible through DOI: 10.5281/zenodo.5559234.
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Mechanisms Governing Target Search and Binding Dynamics of Hypoxia-Inducible FactorsNCBI Gene Expression Omnibus, GSE207575.
Article and author information
Author details
Funding
National Institutes of Health (U54-CA231641-01)
- Xavier Darzacq
Howard Hughes Medical Institute
- Robert Tjian
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2022, Chen et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Mechanisms governing target search and binding dynamics of hypoxia-inducible factors
eLife 11:e75064.
https://doi.org/10.7554/eLife.75064
