In vitro single molecule and bulk phase studies reveal the AP-1 transcription factor cFos binds to DNA without its partner cJun

In vitro single molecule and bulk phase studies reveal the AP-1 transcription factor cFos binds to DNA without its partner cJun

The AP-1 transcription factor family crucially regulates progression of the cell cycle, as well as playing roles in proliferation, differentiation, and the stress response. The two best described AP-1 family members, cFos and cJun, are known to dimerize to form a functional AP-1 heterodimer that bin...

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Bibliographic Details
Published in:The Journal of biological chemistry Vol. 298; no. 8; p. 102229
Main Authors: Leech, James T., Brennan, Andrew, Don, Nicola A., Mason, Jody M., Kad, Neil M.
Format: Journal Article
Language:English
Published: Elsevier Inc 01-08-2022
American Society for Biochemistry and Molecular Biology
Subjects:
AP-1
DNA tightropes
fluorescence
single-molecule
transcription factors
DNA tightropes
CD
single-molecule
mCH
fluorescence
transcription factors
TRE
CRE
mNG
FRET
AP-1
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Summary:The AP-1 transcription factor family crucially regulates progression of the cell cycle, as well as playing roles in proliferation, differentiation, and the stress response. The two best described AP-1 family members, cFos and cJun, are known to dimerize to form a functional AP-1 heterodimer that binds to a consensus response element sequence. Although cJun can also homodimerize and bind to DNA, the canonical view is that cFos cannot bind DNA without heterodimerizing with cJun. Here, we show that cFos can actually bind to DNA in the absence of cJun in vitro. Using dual color single molecule imaging of cFos alone, we directly visualize binding to and movement on DNA. Of all these DNA-bound proteins, detailed analysis suggested 30 to 46% were homodimers. Furthermore, we constructed fluorescent protein fusions of cFos and cJun for Förster resonance energy transfer experiments. These constructs indicated complete dimerization of cJun, but although cFos could dimerize, its extent was reduced. Finally, to provide orthogonal confirmation of cFos binding to DNA, we performed bulk-phase circular dichroism experiments that showed clear structural changes in DNA; these were found to be specific to the AP-1 consensus sequence. Taken together, our results clearly show cFos can interact with DNA both as monomers and dimers independently of its archetypal partner, cJun.
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ISSN:0021-9258
1083-351X
DOI:10.1016/j.jbc.2022.102229