β-Actin and Nuclear Myosin I are responsible for nucleolar reorganization during DNA Repair.

During DNA Repair, ribosomal DNA and RNA polymerase I (rDNA/RNAP1) are reorganized within the nucleolus. Until now, the proteins and the molecular mechanism governing this reorganisation remained unknown.\n\nHere we show that Nuclear Myosin I (NMI) and Nuclear Beta Actin (ACT{beta}) are essential for the proper reorganisation of the nucleolus, after completion of the DNA Repair reaction.\n\nIn NMI and ACT{beta} depleted cells, the rDNA/RNAP1 complex can be displaced at the periphery of the nucleolus after DNA damage but cannot re-enter within the nucleolus after completion of the DNA Repair. Both proteins act concertedly in this process. NMI binds the damaged rDNA at the periphery of the nucleolus, while ACT{beta} brings the rDNA back within the nucleolus after DNA repair completion. Our results reveal a previously unidentified function for NMI and ACT{beta} and disclose how these two proteins work in coordination to re-establish the proper rDNA position after DNA repair.