Abstract
Nuclear membrane rupture during interphase occurs in a variety of cell contexts, both healthy and pathological. In the primary nucleus, membrane ruptures are rapidly repaired but the mechanisms are still unclear. Here we show that BAF, a nuclear envelope protein that shapes chromatin and recruits additional NE proteins in mitosis, also facilitates nuclear membrane repair in interphase, in part through recruitment of the nuclear membrane proteins emerin and LEMD2 to rupture sites. Using a cancer cell line depleted of lamin B1 to drive membrane rupture, we confirmed that GFP-BAF accumulates at rupture sites and found that BAF depletion increased the duration of nucleus integrity loss after rupture, with the largest effects being on longer ruptures. This phenotype could be rescued by WT BAF, but not by a mutant lacking the LEM-protein binding domain. Depletion of LEMD2 or emerin, but not lamin A/C, was sufficient to significantly increase the proportion of long ruptures, consistent with LEM-protein binding being a key function of BAF during membrane repair. Overall our results suggest a membrane repair model where BAF facilitates the repair of large membrane ruptures, in part by recruiting transmembrane nuclear envelope proteins, but where small ruptures are repaired by a BAF-independent mechanism.








