Praja1 protects cells from DNA damage through direct DNA binding

Praja1 is known as an E3 ubiquitin ligase that regulates multiple functions through protein degradation. It acquired nuclear localization signal after gene duplication and although studies have shown some significant roles of nuclear Praja1, comprehensive analysis still lacks. In this study, we performed comparative proteomics and biochemical analyses to elucidate the functions of Praja1 in the nucleus. First, proteomics analysis applied to nuclear localization deficient Praja1 exhibited signs of DNA damage response fluctuation. Subsequent comet assay revealed Praja1 protecting cells from various DNA damage sources. Similarly, cells lacking Praja1 became more sensitive to DNA damage-induced cell death, while E. coli expressing Praja1 exhibited resistance to DNA damage. To further elucidate the molecular basis of DNA protection, gel shift assay showed direct binding of Praja1 to DNA through electrostatic interactions within its intrinsically disordered region. Further in vitro damaging assay suggested that Praja1 may induce structural changes that enhance DNA repair efficiency upon binding to DNA. Together, these results provide insights into the evolutionarily novel role of nuclear Praja1 in protecting against DNA damage.