STIM1 Translocation to The Nucleus Protects Cells from DNA Damage

DNA damage represents a challenge for cells as this damage must be eliminated to preserve cell viability and the transmission of genetic information. To reduce or eliminate unscheduled chemical modifications in genomic DNA, an extensive signaling network, known as the DNA damage response (DDR) pathway, ensures this repair. In this work, and by means of a proteomic analysis aimed at the study of the STIM1 protein interactome, we have found that STIM1 is closely related to the protection from endogenous DNA damage, replicative stress, as well as in the response to interstrand crosslinks (ICLs). Here we show that STIM1 has a nuclear localization signal (NLS) that mediates its translocation to the nucleus, and that this translocation and the association of STIM1 to chromatin is enhanced in response to mitomycin C (MMC), an ICL-inducing agent. Consequently, STIM1-deficient cell lines show a higher level of basal DNA damage, replicative stress, and a higher sensitivity to MMC. We show that STIM1 normalizes FANCD2 protein levels in the nucleus, explaining the increased sensitivity to MMC in STIM1-KO cells. Our results show for the first time a nuclear function for the endoplasmic reticulum protein STIM1 and increase the number of genes involved in DNA repair.