scholarly journals Helicase-Like Transcription Factor HLTF and E3 Ubiquitin Ligase SHPRH Confer DNA Damage Tolerance through Direct Interactions with Proliferating Cell Nuclear Antigen (PCNA)

2020 ◽  
Vol 21 (3) ◽  
pp. 693 ◽  
Author(s):  
Mareike Seelinger ◽  
Marit Otterlei

To prevent replication fork collapse and genome instability under replicative stress, DNA damage tolerance (DDT) mechanisms have evolved. The RAD5 homologs, HLTF (helicase-like transcription factor) and SHPRH (SNF2, histone-linker, PHD and RING finger domain-containing helicase), both ubiquitin ligases, are involved in several DDT mechanisms; DNA translesion synthesis (TLS), fork reversal/remodeling and template switch (TS). Here we show that these two human RAD5 homologs contain functional APIM PCNA interacting motifs. Our results show that both the role of HLTF in TLS in HLTF overexpressing cells, and nuclear localization of SHPRH, are dependent on interaction of HLTF and SHPRH with PCNA. Additionally, we detected multiple changes in the mutation spectra when APIM in overexpressed HLTF or SHPRH were mutated compared to overexpressed wild type proteins. In plasmids from cells overexpressing the APIM mutant version of HLTF, we observed a decrease in C to T transitions, the most common mutation caused by UV irradiation, and an increase in mutations on the transcribed strand. These results strongly suggest that direct binding of HLTF and SHPRH to PCNA is vital for their function in DDT.

2006 ◽  
Vol 26 (14) ◽  
pp. 5509-5517 ◽  
Author(s):  
Takashi Hishida ◽  
Tomoko Ohya ◽  
Yoshino Kubota ◽  
Yusuke Kamada ◽  
Hideo Shinagawa

ABSTRACT Proliferating cell nuclear antigen (PCNA), a sliding clamp required for processive DNA synthesis, provides attachment sites for various other proteins that function in DNA replication, DNA repair, cell cycle progression and chromatin assembly. It has been shown that differential posttranslational modifications of PCNA by ubiquitin or SUMO play a pivotal role in controlling the choice of pathway for rescuing stalled replication forks. Here, we explored the roles of Mgs1 and PCNA in replication fork rescue. We provide evidence that Mgs1 physically associates with PCNA and that Mgs1 helps suppress the RAD6 DNA damage tolerance pathway in the absence of exogenous DNA damage. We also show that PCNA sumoylation inhibits the growth of mgs1 rad18 double mutants, in which PCNA sumoylation and the Srs2 DNA helicase coordinately prevent RAD52-dependent homologous recombination. The proposed roles for Mgs1, Srs2, and modified PCNA during replication arrest highlight the importance of modulating the RAD6 and RAD52 pathways to avoid genome instability.


2020 ◽  
Vol 477 (14) ◽  
pp. 2655-2677
Author(s):  
Li Fan ◽  
Tonghui Bi ◽  
Linxiao Wang ◽  
Wei Xiao

DNA-damage tolerance (DDT) is employed by eukaryotic cells to bypass replication-blocking lesions induced by DNA-damaging agents. In budding yeast Saccharomyces cerevisiae, DDT is mediated by RAD6 epistatic group genes and the central event for DDT is sequential ubiquitination of proliferating cell nuclear antigen (PCNA), a DNA clamp required for replication and DNA repair. DDT consists of two parallel pathways: error-prone DDT is mediated by PCNA monoubiquitination, which recruits translesion synthesis DNA polymerases to bypass lesions with decreased fidelity; and error-free DDT is mediated by K63-linked polyubiquitination of PCNA at the same residue of monoubiquitination, which facilitates homologous recombination-mediated template switch. Interestingly, the same PCNA residue is also subjected to sumoylation, which leads to inhibition of unwanted recombination at replication forks. All three types of PCNA posttranslational modifications require dedicated conjugating and ligation enzymes, and these enzymes are highly conserved in eukaryotes, from yeast to human.


2018 ◽  
Author(s):  
Alison K. Thurston ◽  
Catherine A. Radebaugh ◽  
Adam R. Almeida ◽  
Juan Lucas Argueso ◽  
Laurie A. Stargell

AbstractCells expend a large amount of energy to maintain their DNA sequence. DNA repair pathways, cell cycle checkpoint activation, proofreading polymerases, and chromatin structure are ways in which the cell minimizes changes to the genome. During replication, the DNA damage tolerance pathway allows the replication forks to bypass damage on the template strand. This avoids prolonged replication fork stalling, which can contribute to genome instability. The DNA damage tolerance pathway includes two sub-pathways: translesion synthesis and template switch. Post-translational modification of PCNA and the histone tails, cell cycle phase, and local DNA structure have all been shown to influence sub-pathway choice. Chromatin architecture contributes to maintaining genome stability by providing physical protection of the DNA and by regulating DNA processing pathways. As such, chromatin-binding factors have been implicated in maintaining genome stability. Using Saccharomyces cerevisiae, we examined the role of Spn1, a chromatin binding and transcription elongation factor, in DNA damage tolerance. Expression of a mutant allele of SPN1 results in increased resistance to the DNA damaging agent methyl methanesulfonate, lower spontaneous and damage-induced mutation rates, along with increased chronological lifespan. We attribute these effects to an increased usage of the template switch branch of the DNA damage tolerance pathway in the spn1 strain. This provides evidence for a role of wild type Spn1 in promoting genome instability, as well as having ties to overcoming replication stress and contributing to chronological aging.


Genes ◽  
2018 ◽  
Vol 10 (1) ◽  
pp. 10 ◽  
Author(s):  
Wendy Leung ◽  
Ryan Baxley ◽  
George-Lucian Moldovan ◽  
Anja-Katrin Bielinsky

DNA damage is a constant source of stress challenging genomic integrity. To ensure faithful duplication of our genomes, mechanisms have evolved to deal with damage encountered during replication. One such mechanism is referred to as DNA damage tolerance (DDT). DDT allows for replication to continue in the presence of a DNA lesion by promoting damage bypass. Two major DDT pathways exist: error-prone translesion synthesis (TLS) and error-free template switching (TS). TLS recruits low-fidelity DNA polymerases to directly replicate across the damaged template, whereas TS uses the nascent sister chromatid as a template for bypass. Both pathways must be tightly controlled to prevent the accumulation of mutations that can occur from the dysregulation of DDT proteins. A key regulator of error-prone versus error-free DDT is the replication clamp, proliferating cell nuclear antigen (PCNA). Post-translational modifications (PTMs) of PCNA, mainly by ubiquitin and SUMO (small ubiquitin-like modifier), play a critical role in DDT. In this review, we will discuss the different types of PTMs of PCNA and how they regulate DDT in response to replication stress. We will also cover the roles of PCNA PTMs in lagging strand synthesis, meiotic recombination, as well as somatic hypermutation and class switch recombination.


2010 ◽  
Vol 38 (1) ◽  
pp. 104-109 ◽  
Author(s):  
Alfonso Gallego-Sánchez ◽  
Francisco Conde ◽  
Pedro San Segundo ◽  
Avelino Bueno

Eukaryotes ubiquitylate the replication factor PCNA (proliferating-cell nuclear antigen) so that it tolerates DNA damage. Although, in the last few years, the understanding of the evolutionarily conserved mechanism of ubiquitylation of PCNA, and its crucial role in DNA damage tolerance, has progressed impressively, little is known about the deubiquitylation of this sliding clamp in most organisms. In the present review, we will discuss potential molecular mechanisms regulating PCNA deubiquitylation in yeast.


2018 ◽  
Author(s):  
Qingwen Jiang ◽  
Weimin Zhang ◽  
Chenghao Liu ◽  
Yicong Lin ◽  
Qingyu Wu ◽  
...  

AbstractProliferating cell nuclear antigen (PCNA), encoded by POL30 in Saccharomyces cerevisiae, is a key component of DNA metabolism. Here a library consisting of 308 PCNA mutants was designed and synthesized to probe the contribution of each residue to its biological function. Five regions were identified with elevated sensitivity to DNA damaging reagents using high-throughput phenotype screening. Using a series of genetic and biochemical analyses, we demonstrated that one particular mutant, K168A, which displayed severe DNA damage sensitivity, abolished the DNA damage tolerance (DDT) pathway by disrupting interactions between PCNA and Rad5p. Subsequent domain analysis showed that the PCNA/Rad5p interaction is prerequisite for the function of Rad5p in DDT. Our study not only provides a resource in the form of a library of versatile mutants to study PCNA functions, but also reveals a key regulatory function of Rad5p, which highlights the importance of the PCNA-Rad5p interaction.Author summaryPCNA is regarded as the maestro of DNA replication fork because of the astonishing ability to interact with lots of partner proteins that participate in various DNA metabolism processes. However, it has remained elusive as to how does PCNA orchestrate these functions in harmony. Here, we constructed a systematic mutation library of PCNA, which covers every amino acid to map the functional sites of it. This carefully designed synthetic mutant pool could be generally useful and serve as a flexible resource, such as dissecting the functional mechanism of PCNA by genetic relationship analysis with key proteins through Synthetic genetic array. We further dissected the intrinsic mechanism for damage sensitivity of PCNAK168A, the most severe DNA damage sensitive mutant in our alanine scanning mutation library, this helps us to get better understanding of how PCNA participates in DNA damage tolerance (DDT) pathways. Our findings indicate that K168 site is vital for the interaction between DDT related partner proteins and PCNA, and also highlight the importance of the PCNA-Rad5p interaction.


Genes ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 614 ◽  
Author(s):  
Takuya Abe ◽  
Dana Branzei ◽  
Kouji Hirota

DNA replication is an essential biochemical reaction in dividing cells that frequently stalls at damaged sites. Homologous/homeologous recombination (HR)-mediated template switch and translesion DNA synthesis (TLS)-mediated bypass processes release arrested DNA replication forks. These mechanisms are pivotal for replication fork maintenance and play critical roles in DNA damage tolerance (DDT) and gap-filling. The avian DT40 B lymphocyte cell line provides an opportunity to examine HR-mediated template switch and TLS triggered by abasic sites by sequencing the constitutively diversifying immunoglobulin light-chain variable gene (IgV). During IgV diversification, activation-induced deaminase (AID) converts dC to dU, which in turn is excised by uracil DNA glycosylase and yields abasic sites within a defined window of around 500 base pairs. These abasic sites can induce gene conversion with a set of homeologous upstream pseudogenes via the HR-mediated template switch, resulting in templated mutagenesis, or can be bypassed directly by TLS, resulting in non-templated somatic hypermutation at dC/dG base pairs. In this review, we discuss recent works unveiling IgV diversification mechanisms in avian DT40 cells, which shed light on DDT mode usage in vertebrate cells and tolerance of abasic sites.


2014 ◽  
Vol 289 (19) ◽  
pp. 13627-13637 ◽  
Author(s):  
Claudia M. Nicolae ◽  
Erin R. Aho ◽  
Alexander H. S. Vlahos ◽  
Katherine N. Choe ◽  
Subhajyoti De ◽  
...  

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