MAD2L2 C-terminus is important for its homodimerization and CDH1 binding

MAD2L2 is a central protein in translesion synthesis (TLS) and in mitosis. A central TLS polymerase is Pol zeta (ζ), which is comprised of two subunits, MAD2L2 and Rev3. During TLS, in order to bypass DNA lesions, Pol ζ interacts with the polymerase Rev1. It was recently shown that MAD2L2 forms a homodimer in order to bind Rev3, and the dimerization is essential for TLS function. The dimerization interface includes both the central alpha C helix and the C-terminus β-sheet “crossover” region. The significance of the crossover β-sheet region in homodimerization is still less studied. In addition, MAD2L2 plays an important regulatory role in mitosis, sequestering CDH1 to prevent it from binding prematurely to the anaphase promoting complex/cyclosome (APC/C) and initiating unscheduled mitotic exit. Although the importance of the CDH1-MAD2L2 interaction has been described, the details of the binding mechanism are not yet established. Using a series of C-terminus MAD2L2 mutants, we show that the C-terminus β-sheet interface of MAD2L2 is essential not only for its homodimerization, but also for the CDH1-MAD2L2 binding interaction. Moreover, we generated a CDH1 mutant that lacks the ability to bind MAD2L2, confirming that MAD2L2 interacts with CDH1 in a Rev1-like pattern. Our findings suggest a possible regulatory mechanism of preferential complex formation for MAD2L2 and its binding partners in its various biological roles. Gaining a deeper understanding of the C-terminus binding interface of MAD2L2 will provide further insight into TLS function and cell cycle regulation, and elucidate novel MAD2L2-specific approaches in cancer therapy.