Ubiquitin-Binding Domains in Y-Family Polymerases Regulate Translesion Synthesis

TLDR

Translesion synthesis (TLS) is the primary mechanism for replicating across DNA lesions, and ubiquitination of PCNA directs the replication machinery into TLS, yet the cellular recognition of this modification remains unclear. The study identifies two ubiquitin‑binding domains, UBM and UBZ, that are evolutionarily conserved in all Y‑family TLS polymerases. These domains mediate binding of polη and polι to ubiquitin, their recruitment to replication factories, and interaction with monoubiquitinated PCNA. The UBZ domain of polη is essential for restoring normal UV responses in XP‑V fibroblasts, demonstrating that Y‑family polymerase ubiquitin‑binding domains regulate TLS.

Abstract

Translesion synthesis (TLS) is the major pathway by which mammalian cells replicate across DNA lesions. Upon DNA damage, ubiquitination of proliferating cell nuclear antigen (PCNA) induces bypass of the lesion by directing the replication machinery into the TLS pathway. Yet, how this modification is recognized and interpreted in the cell remains unclear. Here we describe the identification of two ubiquitin (Ub)–binding domains (UBM and UBZ), which are evolutionarily conserved in all Y-family TLS polymerases (pols). These domains are required for binding of polη and polι to ubiquitin, their accumulation in replication factories, and their interaction with monoubiquitinated PCNA. Moreover, the UBZ domain of polη is essential to efficiently restore a normal response to ultraviolet irradiation in xeroderma pigmentosum variant (XP-V) fibroblasts. Our results indicate that Ub-binding domains of Y-family polymerases play crucial regulatory roles in TLS.