The Protein Level of Rev1, a TLS Polymerase in Fission Yeast, Is Strictly Regulated during the Cell Cycle and after DNA Damage.

Masashi Uchiyama,Fumio Hanaoka,Junko Terunuma,Giovanni Maga

doi:10.1371/journal.pone.0130000

Abstract

Translesion DNA synthesis provides an alternative DNA replication mechanism when template DNA is damaged. In fission yeast, Eso1 (polη), Kpa1/DinB (polκ), Rev1, and Polζ (a complex of Rev3 and Rev7) have been identified as translesion synthesis polymerases. The enzymatic characteristics and protein-protein interactions of these polymerases have been intensively characterized; however, how these proteins are regulated during the cell cycle remains unclear. Therefore, we examined the cell cycle oscillation of translesion polymerases. Interestingly, the protein levels of Rev1 peaked during G1 phase and then decreased dramatically at the entry of S phase; this regulation was dependent on the proteasome. Temperature-sensitive proteasome mutants, such as mts2-U31 and mts3-U32, stabilized Rev1 protein when the temperature was shifted to the restrictive condition. In addition, deletion of pop1 or pop2, subunits of SCF ubiquitin ligase complexes, upregulated Rev1 protein levels. Besides these effects during the cell cycle, we also observed upregulation of Rev1 protein upon DNA damage. This upregulation was abolished when rad3, a checkpoint protein, was deleted or when the Rev1 promoter was replaced with a constitutive promoter. From these results, we hypothesize that translesion DNA synthesis is strictly controlled through Rev1 protein levels in order to avoid unwanted mutagenesis.

Highlights

Translesion synthesis (TLS) is a unique DNA damage tolerance pathway in which damaged lesions are replicated using damaged DNA as a template [1]
Rev1 protein levels peaked during the G1 phase of the cell cycle
We examined the oscillation of TLS polymerases in the cell cycle

Summary

Introduction

Translesion synthesis (TLS) is a unique DNA damage tolerance pathway in which damaged lesions are replicated using damaged DNA as a template [1]. Rev can form a complex with Polz [15, 16] These specific protein interactions are thought to ensure appropriate switching of TLS polymerases depending on the type of DNA damage. Monoubiquitinated Rev is reported to associate with FAAP20, an integral subunit of the multisubunit Fanconi anemia core complex [27] These interactions indicate that Rev serves as an important regulator of TLS. Kpa1/DinB has been reported to have a functional interaction with the 9-1-1 complex [30] These reports have described the molecular nature of TLS polymerases from fission yeast, no studies have provided an intensive characterization of the regulation of these TLS polymerases in the cell cycle.

Materials and Methods

Results

Discussion