Regulatory Functions of Ubiquitin and SUMO in DNA Repair Pathways

Ubiquitin and SUMO are structurally related protein modifiers that are covalently attached to lysine residues of target proteins. While ubiquitin is traditionally known as a signal for proteasomal degradation, its nondegradative actions are equally important in the control of cellular key processes. Similarly, the SUMO system primarily acts in a nondegradative manner. Accumulating evidence indicates that these nonproteolytic functions of ubiquitin and SUMO are particularly important in the control of the DNA damage response network, which coordinates a set of DNA repair pathways and allows cells to cope with different types of genotoxic stress. In this chapter we will illustrate some key functions of ubiquitin and SUMO in the control of selected DNA repair pathways.