An ATF4-centric regulatory network is required for the assembly and function of the OXPHOS system

Identifying the factors that determine mammalian cell viability when oxidative phosphorylation (OXPHOS) function is impaired poses challenges due to the diverse cellular responses and limited clinical material availability. Moreover, animal models often fail to replicate human phenotypes. To address these challenges, this study conducted comprehensive analyses involving multiple defects and species by comparing the RNA-Seq expression profiles of human and murine cell lines with distinct nuclear backgrounds, representing both normal and OXPHOS-deficient models. To minimize species-specific variation, the study employed clustering techniques to group murine genes affected by OXPHOS dysfunction and identified crucial regulators like ATF4, UCP1, and SYVN1. ATF4 consistently displayed activation in response to OXPHOS defects, not only in murine but also in human cells, confirming its pivotal role in the cellular response to mitochondrial dysfunction. By integrating human and murine data, the study unveiled a conserved regulatory network encompassing genes related to the mTOR pathway and folate metabolism. Remarkably, the study uncovered an unexpected finding: the depletion of ATF4 in both mouse and human cells impairs OXPHOS assembly and supercomplex organization. This impairment primarily stems from a severe disruption in complex I assembly in the absence of ATF4, even under non-stress conditions.