Deletion of TLS polymerases promotes homologous recombination in Arabidopsis

Abstract

Unrepaired DNA damage hinders the maintenance of genome integrity because it blocks the catalytic activity of replicase. The stalled replication fork can be processed through either translesion synthesis (TLS) with specific polymerases, or replication using the undamaged template. To investigate how TLS activities are regulated and how the stalled replication fork is processed in plants, reversion frequencies and homologous recombination (HR) frequencies were analyzed using GUS-based substrates. The HR frequencies in plants deficient in DNA polymerase ζ (Pol ζ) or Rev1 were higher than that in wildtype plants under normal conditions, and were significantly increased by ultraviolet light irradiation. Heat shock protein (HSP) 90 is known to be involved in various stress responses. To examine the role of HSP90 in the regulation of damage tolerance, we analyzed reversion frequencies and HR frequencies in plants grown in the presence of a HSP inhibitor, geldanamycin (GDA). Reversion frequency was lower in GDA-treated plants than in mock-treated plants. Though the HR frequency was higher in GDA-treated wildtype plants than in mock-treated plants, no significant difference was detected in Rev1-deficient plants. In yeast, TLS polymerases interacted with each other or with a replication clump component, proliferating cell nuclear antigen (PCNA). HSP90 interacted with REV1 or REV7 in Nicotiana benthamiana cells. These results suggest that HSP90 interacts with TLS polymerase(s), which promotes error-prone TLS in plants.

Translesion Synthesis in Plants: Ultraviolet Resistance and Beyond

“…Conversely, in HsPolη-deficient cells, 17-AAG treatment reduces mutation due to the inhibition of the REV1-dependent error-prone bypass (Pozo et al, 2011). In contrast with the results in mammals, treatment with geldanamycin reduces mutation frequencies in wild-type plants, which are AtPolη-proficient (Sakamoto et al, 2018). This suggests that HSP90 mainly regulates the error-prone TLS pathway, involving AtRev1, in Arabidopsis .…”

“…Both Arabidopsis PCNAs interact with ubiquitin in N. benthamiana cells and are ubiquitinated in vitro (Strzalka et al, 2013). The AtREV1 interacts with PCNA2, AtPolη, and AtREV7, a regulatory subunit of AtPolζ in yeast (Sakamoto et al, 2018). The processivity of rice Polλ is stimulated in the presence of PCNA (Uchiyama et al, 2004).…”

“…The rad5a plant failed to induce homologous recombination events after bleomycin treatment (Chen et al, 2008). By contrast, rev3 and rev1 plants induced significantly more recombination events after UV irradiation (Sakamoto et al, 2018). If AtRAD5a and AtREV3 work via two alternative pathways, the elevation of recombination activities in rev3 and rev1 plant could be due to the activation of a RAD5-dependent pathway ( Figure 1D ).…”

“…Crystal structure and NMR analyses showed that two copies of REV7 bind to the canonical REV7-binding motifs (RBMs) of REV3 (Rizzo et al, 2018). In plants, Arabidopsis REV7 makes a homodimer in both the nucleus and the cytosol (Sakamoto et al, 2018). However, there is only one repeat of RBM in AtREV3 sequences, which is similar to yeast REV3 (Tomida et al, 2015).…”

The Dark Side of UV-Induced DNA Lesion Repair

“…Based on the models of a CPDs and 6-4 PPs bypass in plants it was postulated that UV-induced mutations observed in Arabidopsis might be caused by a mutagenic bypass of TT 6-4 PPs by AtREV1 and AtPOLζ [239]. Recent studies indicate that similarly to mammals, AtHSP90 positively regulates the activity of the TLS pathway in Arabidopsis [240]. Replicative polymerase complex (either pol δ or pol ε) are blocked by a CPD or 6-4 PP DNA lesion (a).…”