GIP1 and GIP2 Contribute to the Maintenance of Genome Stability at the Nuclear Periphery

The maintenance of genetic information is important in eukaryotes notably through mechanisms occurring at the nuclear periphery where inner nuclear membrane proteins and nuclear pore-associated components are key factors regulating the DNA damage response (DDR). However, this aspect of DDR regulation is still poorly documented in plants. We addressed here how genomic stability is impaired in the gamma-tubulin complex component 3-interacting protein (gip1gip2) double mutants showing defective nuclear shaping. Using neutral comet assays for DNA double-strand breaks (DSBs) detection, we showed that GIP1 and GIP2 act redundantly to maintain genome stability. At the cellular level, gamma-H2AX foci in gip1gip2 were more abundant and heterogeneous in their size compared to wild-type (WT) in root meristematic nuclei, indicative of constitutive DNA damage. This was linked to a constitutive activation of the DDR in the gip1gip2 mutant, with more emphasis on the homologous recombination (HR) repair pathway. In addition, we noticed the presence of numerous RAD51 foci which did not colocalize with gamma-H2AX foci. The expression of GIP1-GFP in the double mutant rescued the cellular response to DNA damage, leading to the systematic colocalization of RAD51 and gamma-H2AX foci. Interestingly, a significant proportion of RAD51 foci colocalized with GIP1-GFP at the nuclear periphery. Altogether, our data suggest that GIPs may partly contribute to the spatio-temporal recruitment of RAD51 at the nuclear periphery.

Automated summary

This study investigates the role of inner nuclear membrane proteins and nuclear pore-associated components in maintaining genetic stability in plants. The gamma-tubulin complex component 3-interacting protein (gip1gip2) double mutants with defective nuclear shaping were used as a model. The results show that GIP1 and GIP2 play redundant roles in maintaining genome stability, with defects in these proteins leading to constitutive DNA damage and activation of the DNA damage response. Furthermore, the expression of GIP1-GFP in the mutants rescues the cellular response to DNA damage and promotes the colocalization of RAD51 and gamma-H2AX foci, suggesting the involvement of GIPs in the spatio-temporal recruitment of RAD51 at the nuclear periphery.