Adding ubiquitin to a nuclear pore protein promotes repair of damaged DNA, Niño et al. show.
The functions of nuclear pore complexes extend far beyond transportation into and out of the nucleus. They help organize the genome, manage gene expression, monitor mRNA quality, and stimulate repair of damaged DNA. Posttranslational modifications of nucleoporins (Nups) may help multitasking pores coordinate all of their responsibilities. Niño et al. focused on modifications of one Nup, Nup60, which is part of the basket structure on the pore’s nuclear side.
The researchers discovered that Nup60 was ubiquitylated and SUMOylated. Neither modification was necessary for the protein to attach to the pore. However, a version of Nup60 that couldn’t be ubiquitylated was more dynamic, rapidly detaching from the pore complex with its partner Nup2. Preventing SUMOylation, in contrast, had no effect on Nup60’s dynamics. Niño et al. determined that ubiquitylated Nup60 attaches to the Y complex, a building block of the nuclear pore, likely by binding to a component of the Y complex named Nup84.
How does ubiquitylation of Nup60 alter its function? The researchers found that the modification had no effect on the movement of cargoes through the pore. Instead, their results revealed a role in DNA repair. They found that Nup60 ubiquitylation increased in cells exposed to a DNA-damaging chemical. Cells carrying Nup60 that can’t be ubiquitylated displayed a less efficient DNA damage response.
How Nup60 fosters DNA repair remains to be determined. The researchers suggest that Nup60’s ubiquitylation might alter the dynamics of the nuclear pore basket and create a protected environment that favors DNA repair.