Spatiotemporal regulation of PCNA ubiquitination in damage tolerance pathways

Abstract

DNA is constantly exposed to a wide variety of exogenous and endogenous agents, and most DNA lesions inhibit DNA synthesis. To cope with such problems during replication, cells have molecular mechanisms to resume DNA synthesis in the presence of DNA lesions, which are known as DNA damage tolerance (DDT) pathways. The concept of ubiquitination-mediated regulation of DDT pathways in eukaryotes was established via genetic studies in the yeast Saccharomyces cerevisiae, in which two branches of the DDT pathway are regulated via ubiquitination of proliferating cell nuclear antigen (PCNA): translesion DNA synthesis (TLS) and homology-dependent repair (HDR), which are stimulated by mono-and polyubiquitination of PCNA, respectively. Over the subsequent nearly two decades, significant progress has been made in understanding the mechanisms that regulate DDT pathways in other eukaryotes. Importantly, TLS is intrinsically error-prone because of the miscoding nature of most damaged nucleotides and inaccurate replication of undamaged templates by TLS polymerases (pols), whereas HDR is theoretically error-free because the DNA synthesis is thought to be predominantly performed by pol d, an accurate replicative DNA pol, using the undamaged sister chromatid as its template. Thus, the regulation of the choice between the TLS and HDR pathways is critical to determine the appropriate biological outcomes caused by DNA damage. In this review, we summarize our current understanding of the species-specific regulatory mechanisms of PCNA ubiquitination and how cells choose between TLS and HDR. We then provide a hypothetical model for the spatiotemporal regulation of DDT pathways in human cells.

Complex Mechanisms of Antimony Genotoxicity in Budding Yeast Involves Replication and Topoisomerase I-Associated DNA Lesions, Telomere Dysfunction and Inhibition of DNA Repair

“…In S phase, ssDNA gaps are preferentially repaired by a recombination-like mechanism called template switch (TS) that depends on the Rad18 and Rad5 E3 ubiquitin ligases, recombination proteins, including Rad51 and Rad52, and nucleases such as the Sgs1-Top3-Rmi1 (STR) complex [ 54 ]. In G2 phase, ssDNA gaps can be also filled by one of translesion synthesis (TLS) low-fidelity polymerases in a Rad18-depedendent manner [ 55 ]. In budding yeast, DSBs are predominantly repaired by homologous recombination (HR) with only a minor role of non-homologous end joining (NHEJ) that depends on the yKU (Yku70-Yku80) complex and the DNA ligase IV Dnl4 [ 56 , 57 ].…”

“…We also showed that Sb(III) causes perturbation of DNA synthesis leading to formation of ssDNA regions, which may correspond to stalled replication forks and/or ssDNA gaps formed behind the fork as a result of damage bypass ( Figure 3 E or Figure 5 B). Post-replication repair of ssDNA gaps requires two ubiquitin ligases Rad18 and Rad5 as well as HR proteins [ 54 , 55 ]. Consistently, rad18 Δ and rad5 Δ mutants were more sensitive to Sb(III) compared to wild-type ( Figure 1 ).…”

Application of Modified Closed Biopsy in Rabbit Model of VX2 Transplanted Bone Tumor

“…PCNA surrounds and slides along the DNA in the nucleus. DNA polymerase, helicase, exonuclease, ligase, cell cycle regulator, acetyltransferase, chromatin reconstitution and histone chaperone interact with DNA by binding with PCNA [22] PCNA was expressed in all cell cycles of normal tissues, and its expression level was relatively stable [23]. Some rabbit experiments [24] showed that the level of PCNA expression was signi cantly reduced by the stimulation of traumatic factors.…”

Replication Fork Remodeling and Therapy Escape in DNA Damage Response-Deficient Cancers

“…In yeast, this modification is carried out by the E2-E3 complex Rad6-Rad18. In humans, however, several proteins seem to be implicated and their dynamics is not fully understood yet (186). Preferentially, the mono-ubiquitin mark would be extended to a poly-ubiquitin chain in a UBC13-dependent manner to stimulate ZRANB3-driven RF reversal and the error-free TS pathway in early S-phase (100,103,187,188).…”