**Abstract**

The system of base excision repair (BER) evolved to correct the most abundant DNA damages in mammalian cells is the most essential for maintaining the genome integrity. The multistep BER process involves several enzymes and protein factors functioning in a coordinated fashion that ensures the repair efficiency. The coordination is facilitated by the formation of protein complexes stabilized via either direct or indirect DNA-mediated interactions. This review focuses on direct interactions of proteins participating in BER with each other and with noncanonical factors found recently to modulate the efficiency of BER. All the known partners of main BER participants, the sites responsible for their interaction, and the characteristics of protein-protein affinity are summarized. Well-documented evidences of how DNA intermediates and posttranslational modifications of proteins modulate protein-protein interactions are presented. The available data allow to suggest that the multiprotein complexes are assembled with the involvement of a scaffold protein XRCC1 and poly(ADP-ribose) polymerase 1, a key regulator of the BER process, irrespective of the DNA damage; the composition and the structure of the complexes are dynamically changed depending on the DNA damage, its chromatin environment, and the step of BER process.

**Keywords:** base excision repair, protein-protein interactions, noncanonical factors, posttranslational modifications of proteins, coordination of DNA repair
