Inhibition of the PP2A activity by the histone chaperone ANP32B is long-range allosterically regulated by respiratory cytochrome c

17 pags., 9 figs., 1 tab.
Repair of injured DNA relies on nucleosome dismantling by histone chaperones and de-phosphorylation events carried out by Protein Phosphatase 2A (PP2A). Typical histone chaperones are the Acidic leucine-rich Nuclear Phosphoprotein 32 family (ANP32) members, e.g. ANP32A, which is also a well-known PP2A inhibitor (a.k.a. IPP2A). Here we report the novel interaction between the endogenous family member B—so-called ANP32B—and endogenous cytochrome c in cells undergoing camptothecin-induced DNA damage. Soon after DNA lesions but prior to caspase cascade activation, the hemeprotein translocates to the nucleus to target the Low Complexity Acidic Region (LCAR) of ANP32B; in a similar way, our group recently reported that the hemeprotein targets the acidic domain of SET/Template Activating Factor-Iβ (SET/TAF-Iβ), which is another histone chaperone and PP2A inhibitor (a.k.a. IPP2A). The nucleosome assembly activity of ANP32B is indeed unaffected by cytochrome c binding. Like ANP32A, ANP32B inhibits PP2A activity and is thus herein referred to as IPP2A. Our data demonstrates that ANP32B-dependent inhibition of PP2A is regulated by respiratory cytochrome c, which induces long-distance allosteric changes in the structured N-terminal domain of ANP32B upon binding to the C-terminal LCAR. In agreement with the reported role of PP2A in the DNA damage response, we propose a model wherein cytochrome c is translocated from the mitochondria into the nucleus upon DNA damage to modulate PP2A activity via its interaction with ANP32B.
This work was supported by the Spanish Ministry of Science, Innovation and Universities (BFU2012-31670, BFU2015-71017, PGC2018-096049- BI00), Spanish Ministry of Education and Professional Training (FPU013/04373 to FRR, FPU016/01513 to AVC), Regional Government of Andalusia (BIO198, US-1254317 US/JUNTA/FEDER,UE, US- 1257019 US/JUNTA/FEDER,UE, P18-FR-3487 and P18–HO-4091), Ramon Areces Foundation, Biointeractomics Platform (cicCartuja, Seville) and the Microscopy and NMR Services at CITIUS (University of Seville). MPG is funded by a postdoctoral grant from the Spanish Association Against Cancer Scientific Foundation (FC AECC)