Magnitov, M. D.; Maresca, M.; Alonso Saiz, N.; Teunissen, H.; Braccioli, L.; de Wit, E.

Gene expression is orchestrated by transcription factors, which function within the context of a three-dimensional genome. Zinc finger protein 143 (ZNF143/ZFP143) is a transcription factor that has been implicated in both gene activation and chromatin looping. To study the direct consequences of ZNF143/ZFP143 loss, we generated a ZNF143/ZFP143 degron line. Our results show that ZNF143/ZFP143 depletion has no effect on chromatin looping. Systematic analysis of ZNF143/ZFP143 occupancy data revealed that a commonly used antibody cross-reacts with CTCF, leading to its incorrect association with chromatin loops. Nevertheless, ZNF143/ZFP143 specifically activates nuclear-encoded mitochondrial genes and its loss leads to severe mitochondrial dysfunction. Using an in vitro embryo model, we find that ZNF143/ZFP143 is an essential regulator of organismal development. Our results establish ZNF143/ZFP143 as a conserved transcriptional regulator of cell proliferation and differentiation by safeguarding mitochondrial activity.