Coupled MD simulations and NMR reveal that the intrinsically disordered domain of the breast-cancer susceptibility 1 protein (BRCA1) binds head-on to DNA double-strand ends

Che, Kateryna; Kress, Thomas J.; Górka, Michał; Żerko, Szymon; Koźmiński, Wiktor; Kurzbach, Dennis

doi:10.1016/j.jmro.2022.100069

Cited by 1 publication

(3 citation statements)

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“…In our earlier work, we found that the employed BRCA1 219-504 fragment binds to the EBOX DNA hexamer. 29 Hence, competition for the DNA with MAX is very likely the underlying reason for the observed effect.…”

Section: Resultsmentioning

confidence: 98%

“…The cells were resuspended in M9 (with homogeneously 13 C labeled glucose 1 g/L and 15 N ammonium chloride 1 g/L) before induction through IPTG. The expression was carried out overnight at 30° C. While for BRCA1 and MAX we followed the procedures reported in 29 and 31 , respectively, MYC was produced employing a protocol for insoluble proteins. The cells were disrupted, and the insoluble fraction was resuspended in denaturing buffer (25 mM Tris, 100 mM NaCl, 6 M GuCl, pH 8.0) overnight.…”

Section: Protein Expression and Sample Preparationmentioning

confidence: 99%

“…Speci cally, the intrinsically disordered region of BRCA1, spanning amino acids ~ 200 to ~ 500, interacts with both MYC and its consensus DNA sequence housing the CACGTG EBOX motif. 29 The modulation of MYC by BRCA1 is furthermore linked to MYC overexpression in BRCA1-associated HBOC. 25 In contrast, BRCA1 is not associated with direct MAX binding, despite the latter's high sequence similarity with MYC.…”

Section: Introductionmentioning

confidence: 99%

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BRCA1 inhibits MYC:MAX heterodimerization by modulating the availability of transient MAX monomers

Kurzbach

Epasto²,

Pötzl³

et al. 2023

Preprint

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The breast cancer susceptibility protein 1 (BRCA1) plays a pivotal role in inhibiting the transcriptional activity of the proto-oncogenic intrinsically disordered protein MYC. By direct binding to MYC, BRCA1 blocks its activation by the MYC-associated factor X (MAX) and the formation of the vital MYC:MAX complex. In contrast, BRCA1 is not associated with binding to the MAX. In this study, we demonstrate a previously undisclosed influence of BRCA1 on MYC:MAX activity. By employing simultaneously time- and residue-resolved nuclear magnetic resonance (NMR) spectroscopy, integrated with MD simulations and EPR spectroscopy, we provide evidence for two subtle regulatory mechanisms: 1. BRCA1 competes with MAX:MAX dimers for DNA ligands, which leads to a destabilization of the native DNA-bound form of the homodimer. 2. BRCA1 binds not only MYC to impede its heterodimerization and transcriptional activity, but it also occupies MAX, when dissociated into its uncommon monomeric form. This conformation is an intermediate that occurs transiently before heterodimerization with MYC. We demonstrate that the MAX monomer, much like MYC, forms highly dynamic complexes with BRCA1, which efficiently block both interaction partners. This discovery is rationalized by the fact that MYC and MAX monomers both lack a stable secondary and tertiary structure (so-called intrinsically disordered proteins) but display high sequence similarity. Both the abovementioned mechanisms balance each other. While the competition for DNA ligands (mechanism 1) promotes MYC:MAX formation, occupation of MAX (and MYC) by BRCA1 (mechanism 2) impedes it. Under the in-vitro conditions probed herein, i.e., an excess of BRCA1, the latter yet dominates, slowing down the MYC:MAX dimerization event and, thus, providing a potential mechanism for downregulation of its transcriptional efficacy. Since the deregulation of BRCA1 activity is directly linked to hereditary breast and ovarian cancer, our findings might open unconventional routes toward novel prevention strategies.

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Section: Resultsmentioning

confidence: 98%