Characterization of an Hsp90-Independent Interaction between Co-Chaperone p23 and Transcription Factor p53

Abstract

Cancer-suppressing transcription factor p53 is regulated by a wide variety of cellular factors, including many chaperones. The DNA-binding domain (DBD) of p53 is known to interact with the chaperone Hsp90, but the role of other members of the chaperone network, including co-chaperones such as p23, is unknown. Using a combination of nuclear magnetic resonance (NMR) titration, isothermal titration calorimetry, fluorescence anisotropy, and native agarose gel electrophoresis, we have identified a direct interaction between the p53 DBD and Hsp90 co-chaperone p23 that occurs in the absence of Hsp90. The affinity is relatively weak and largely determined by electrostatic interactions between the acidic C-terminal disordered tail of p23 and the two DNA-binding regions of the p53 DBD. We show by NMR and native agarose gel electrophoresis that a p53-specific double-stranded DNA sequence competes successfully with p23 for binding to the p53 DBD. The Hsp90 independence of the interaction between p23 and p53 DBD, together with the competition of p23 versus DNA for p53, raises the intriguing possibility that p23, like other small charged proteins, may affect p53 in hitherto unknown ways.

Structure, Function, and Regulation of the Hsp90 Machinery

“…In addition to the central role p23/Sba1 plays in the Hsp90 cycle, p23/Sba1 also exerts Hsp90-independent functions. These include chromatin remodeling, ribosome biogenesis (Echtenkamp et al 2011(Echtenkamp et al , 2016, and Hsp90-independent interaction with tumor-suppressor protein 53 ( p53), which is supposed to compete with its DNA binding (Wu et al 2018).…”

“…Sti1/Hop was found to be overexpressed in certain cancers (Chao et al 2013;Carvalho da Fonseca et al 2014) and to promote invasion when present in the extracellular space (Walsh et al 2011). Interestingly, mutated p53 seems to induce the expression of Sti1/Hop (Mattison et al 2017) and p23 was shown to directly bind and modulate p53 in a Hsp90-independent manner (Wu et al 2018). Silencing of Cdc37 destabilized kinases and thus, sensitized cancer cells to Hsp90 inhibition (Smith et al 2009).…”

Anticancer properties and mechanism of action of the quassinoid ailanthone

“…We can foresee other consequences of the binding of AIT to p23 because this cochaperone has been shown to bind to the DNA‐binding domain (DBD) of p53, as it is the case for Hsp90 (Wu, Hyun, Martinez‐Yamout, Park, & Dyson, 2018). This raises the intriguing possibility that p23 affects the cancer‐suppressing transcription factor p53 and that AIT modulates this function.…”

Aggregation of zinc‐free p53 is inhibited by Hsp90 but not other chaperones

“…Human Hsp90α, 4,19 p53(88-312), 3,19 p23, 19,20 Hsp70, 21 Hsp40, 22 and HOP 23 were prepared as described previously. The published preparation of 15 N-labeled p53 yields the folded, zinc-bound form.…”

“…Native agarose gel electrophoresis was used to investigate protein-protein interactions using published protocols. 19,24 Typically, a 50-100 μM p53 sample was analyzed with binding partners Hsp90 and p23 at concentration ratios ranging from 0:0 to 2:0 or 2.5:0. Zinc binding to apo p53 DBD was analyzed using concentration ratios (zinc sulfate:apo p53 DBD) from 0:0 to 20:0.…”