scholarly journals PCNA Ubiquitylation: Instructive or Permissive to DNA Damage Tolerance Pathways?

Biomolecules ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1543
Author(s):  
Jun Che ◽  
Xin Hong ◽  
Hai Rao
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Damage Tolerance ◽  
Translesion Synthesis ◽  
Dna Lesions ◽  
Template Switching ◽  
Dna Damage Tolerance ◽  
Future Studies ◽  
Dna Lesion ◽  
Replicative Polymerases

DNA lesions escaping from repair often block the DNA replicative polymerases required for DNA replication and are handled during the S/G2 phases by the DNA damage tolerance (DDT) mechanisms, which include the error-prone translesion synthesis (TLS) and the error-free template switching (TS) pathways. Where the mono-ubiquitylation of PCNA K164 is critical for TLS, the poly-ubiquitylation of the same residue is obligatory for TS. However, it is not known how cells divide the labor between TLS and TS. Due to the fact that the type of DNA lesion significantly influences the TLS and TS choice, we propose that, instead of altering the ratio between the mono- and poly-Ub forms of PCNA, the competition between TLS and TS would automatically determine the selection between the two pathways. Future studies, especially the single integrated lesion “i-Damage” system, would elucidate detailed mechanisms governing the choices of specific DDT pathways.

scholarly journals Monoubiquitylation of histone H2B contributes to the bypass of DNA damage during and after DNA replication

2017 ◽  
Vol 114 (11) ◽  
pp. E2205-E2214 ◽  
Author(s):  
Shih-Hsun Hung ◽  
Ronald P. Wong ◽  
Helle D. Ulrich ◽  
Cheng-Fu Kao
Keyword(s):  
Dna Damage ◽  
Replication Fork ◽  
Dna Lesions ◽  
Template Switching ◽  
Lesion Bypass ◽  
Dna Damage Tolerance ◽  
Cytological Evidence ◽  
Histone H2b ◽  
Chromatin Dynamics ◽  
Dna Lesion

DNA lesion bypass is mediated by DNA damage tolerance (DDT) pathways and homologous recombination (HR). The DDT pathways, which involve translesion synthesis and template switching (TS), are activated by the ubiquitylation (ub) of PCNA through components of the RAD6-RAD18 pathway, whereas the HR pathway is independent of RAD18. However, it is unclear how these processes are coordinated within the context of chromatin. Here we show that Bre1, an ubiquitin ligase specific for histone H2B, is recruited to chromatin in a manner coupled to replication of damaged DNA. In the absence of Bre1 or H2Bub, cells exhibit accumulation of unrepaired DNA lesions. Consequently, the damaged forks become unstable and resistant to repair. We provide physical, genetic, and cytological evidence that H2Bub contributes toward both Rad18-dependent TS and replication fork repair by HR. Using an inducible system of DNA damage bypass, we further show that H2Bub is required for the regulation of DDT after genome duplication. We propose that Bre1-H2Bub facilitates fork recovery and gap-filling repair by controlling chromatin dynamics in response to replicative DNA damage.

scholarly journals DNA damage tolerance in stem cells, ageing, mutagenesis, disease and cancer therapy

2019 ◽  
Vol 47 (14) ◽  
pp. 7163-7181 ◽  
Author(s):  
Bas Pilzecker ◽  
Olimpia Alessandra Buoninfante ◽  
Heinz Jacobs
Keyword(s):  
Dna Damage ◽  
Dna Damage Response ◽  
Damage Tolerance ◽  
Essential Feature ◽  
Dna Lesions ◽  
Template Switching ◽  
Dna Damage Tolerance ◽  
Response Network ◽  
Damage Response ◽  
Fork Stalling

AbstractThe DNA damage response network guards the stability of the genome from a plethora of exogenous and endogenous insults. An essential feature of the DNA damage response network is its capacity to tolerate DNA damage and structural impediments during DNA synthesis. This capacity, referred to as DNA damage tolerance (DDT), contributes to replication fork progression and stability in the presence of blocking structures or DNA lesions. Defective DDT can lead to a prolonged fork arrest and eventually cumulate in a fork collapse that involves the formation of DNA double strand breaks. Four principal modes of DDT have been distinguished: translesion synthesis, fork reversal, template switching and repriming. All DDT modes warrant continuation of replication through bypassing the fork stalling impediment or repriming downstream of the impediment in combination with filling of the single-stranded DNA gaps. In this way, DDT prevents secondary DNA damage and critically contributes to genome stability and cellular fitness. DDT plays a key role in mutagenesis, stem cell maintenance, ageing and the prevention of cancer. This review provides an overview of the role of DDT in these aspects.

scholarly journals Mechanisms of DNA Damage Tolerance: Post-Translational Regulation of PCNA

Genes ◽  
2018 ◽  
Vol 10 (1) ◽  
pp. 10 ◽  
Author(s):  
Wendy Leung ◽  
Ryan Baxley ◽  
George-Lucian Moldovan ◽  
Anja-Katrin Bielinsky
Keyword(s):  
Dna Damage ◽  
Translational Regulation ◽  
Damage Tolerance ◽  
Somatic Hypermutation ◽  
Critical Role ◽  
Nuclear Antigen ◽  
Template Switching ◽  
Dna Damage Tolerance ◽  
Class Switch ◽  
Dna Lesion

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.

scholarly journals The homologous recombination complex of the Rad51 paralogs Rad55-Rad57 avoids translesion DNA polymerase recruitment and counterbalances mutagenesis induced by UV radiation

2021 ◽  
Author(s):  
Laurent G Maloisel ◽  
Emilie Ma ◽  
Eric Coic
Keyword(s):  
Homologous Recombination ◽  
Uv Radiation ◽  
Dna Lesions ◽  
Template Switching ◽  
Dna Double Strand Breaks ◽  
Dna Damage Tolerance ◽  
Strand Breaks ◽  
Rad51 Paralogs ◽  
Replicative Polymerases ◽  
Stalled Replication Forks

Bypass of DNA lesions that block replicative polymerases during DNA replication relies on several DNA damage tolerance pathways. The error-prone translesion synthesis (TLS) pathway involves specialized DNA polymerases that incorporate nucleotides in front of base lesions. The template switching and the homologous recombination (HR) pathways are mostly error-free because the bypass is performed by using typically the sister chromatid as a template. This is promoted by the Rad51 recombinase that forms nucleoprotein filaments on single-strand DNA (ssDNA). The balance between error-prone and error-free pathways controls the level of mutagenesis. In yeast, the Rad55-Rad57 complex of Rad51 paralogs is required for Rad51 filament formation and stability, notably by counteracting the Srs2 antirecombinase. Several reports showed that Rad55-Rad57 promotes HR at stalled replication forks more than at DNA double-strand breaks (DSB), suggesting that this complex is more efficient at ssDNA gaps and thus, could control the recruitment of TLS polymerases. To address this point, we studied the interplay between Rad55-Rad57 and the TLS polymerases Polζ and Polη following UV radiation. We confirmed that Rad55-Rad57 protects Rad51 filaments from Srs2 dismantling activity but we found that it is also essential for the promotion of UV-induced HR independently of Srs2. In addition, we observed that cell UV sensitivity, but not DSB sensitivity, is synergistically increased when Rad55 and Polζ deletions are combined. Moreover, we found that mutagenesis and HR frequency were increased in rad55∆ mutants and in TLS-deficient cells, respectively. Finally, UV-induced HR was partially restored in Rad55-deficient cells with mutated Polζ or Polη. Overall, our data suggest that the HR and TLS pathways compete for the same ssDNA substrates and that the Rad55-Rad57 complex of Rad51 paralogs prevents the recruitment of TLS polymerases and counterbalances mutagenesis.

scholarly journals The Mgs1/WRNIP1 ATPase is required to prevent a recombination salvage pathway at damaged replication forks

2020 ◽  
Vol 6 (15) ◽  
pp. eaaz3327 ◽  
Author(s):  
Alberto Jiménez-Martín ◽  
Irene Saugar ◽  
Chinnu Rose Joseph ◽  
Alexandra Mayer ◽  
Carl P. Lehmann ◽  
...  
Keyword(s):  
Dna Damage ◽  
Genome Stability ◽  
Dna Lesions ◽  
Template Switching ◽  
Replication Forks ◽  
Salvage Pathway ◽  
Dna Damage Tolerance ◽  
Alternative Mode ◽  
Free Mode ◽  
Template Switch

DNA damage tolerance (DDT) is crucial for genome integrity maintenance. DDT is mainly carried out by template switch recombination, an error-free mode of overcoming DNA lesions, or translesion DNA synthesis, which is error-prone. Here, we investigated the role of Mgs1/WRNIP1 in modulating DDT. Using budding yeast, we found that elimination of Mgs1 in cells lacking Rad5, an essential protein for DDT, activates an alternative mode of DNA damage bypass, driven by recombination, which allows chromosome replication and cell viability under stress conditions that block DNA replication forks. This salvage pathway is RAD52 and RAD59 dependent, requires the DNA polymerase δ and PCNA modification at K164, and is enabled by Esc2 and the PCNA unloader Elg1, being inhibited when Mgs1 is present. We propose that Mgs1 is necessary to prevent a potentially toxic recombination salvage pathway at sites of perturbed replication, which, in turn, favors Rad5-dependent template switching, thus helping to preserve genome stability.

scholarly journals Elevated Hedgehog activity contributes to attenuated DNA damage responses in aged hematopoietic cells

Leukemia ◽  
2019 ◽  
Vol 34 (4) ◽  
pp. 1125-1134
Author(s):  
Annika Scheffold ◽  
Ali H. Baig ◽  
Zhiyang Chen ◽  
Sarah E. von Löhneysen ◽  
Friedrich Becker ◽  
...  
Keyword(s):  
Dna Damage ◽  
Therapeutic Strategy ◽  
Damage Tolerance ◽  
Dna Lesions ◽  
Hematopoietic Progenitors ◽  
Dna Damage Tolerance ◽  
Hematopoietic System ◽  
Dna Damage Responses ◽  
Underlying Mechanisms ◽  
Bulky Dna Lesions

AbstractAccumulation of DNA damage and myeloid-skewed differentiation characterize aging of the hematopoietic system, yet underlying mechanisms remain incompletely understood. Here, we show that aging hematopoietic progenitor cells particularly of the myeloid branch exhibit enhanced resistance to bulky DNA lesions—a relevant type of DNA damage induced by toxins such as cancer drugs or endogenous aldehydes. We identified aging-associated activation of the Hedgehog (Hh) pathway to be connected to this phenotype. Inhibition of Hh signaling reverts DNA damage tolerance and DNA damage-resistant proliferation in aged hematopoietic progenitors. Vice versa, elevating Hh activity in young hematopoietic progenitors is sufficient to impair DNA damage responses. Altogether, these findings provide experimental evidence for aging-associated increases in Hh activity driving DNA damage tolerance in myeloid progenitors and myeloid-skewed differentiation. Modulation of Hh activity could thus be explored as a therapeutic strategy to prevent DNA damage tolerance, myeloid skewing, and disease development in the aging hematopoietic system.

scholarly journals Error-Free DNA Damage Tolerance and Sister Chromatid Proximity during DNA Replication Rely on the Polα/Primase/Ctf4 Complex

2015 ◽  
Vol 57 (5) ◽  
pp. 812-823 ◽  
Author(s):  
Marco Fumasoni ◽  
Katharina Zwicky ◽  
Fabio Vanoli ◽  
Massimo Lopes ◽  
Dana Branzei
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Sister Chromatid ◽  
Damage Tolerance ◽  
Dna Damage Tolerance ◽  
Free Dna

scholarly journals Non-Recombinogenic Functions of Rad51, BRCA2, and Rad52 in DNA Damage Tolerance

Genes ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1550
Author(s):  
Félix Prado
Keyword(s):  
Dna Damage ◽  
Homologous Recombination ◽  
Damage Tolerance ◽  
Molecular Switches ◽  
Strand Exchange ◽  
Template Switching ◽  
Replication Forks ◽  
Lesion Bypass ◽  
Dna Damage Tolerance ◽  
Exchange Activity

The DNA damage tolerance (DDT) response is aimed to timely and safely complete DNA replication by facilitating the advance of replication forks through blocking lesions. This process is associated with an accumulation of single-strand DNA (ssDNA), both at the fork and behind the fork. Lesion bypass and ssDNA filling can be performed by translation synthesis (TLS) and template switching mechanisms. TLS uses low-fidelity polymerases to incorporate a dNTP opposite the blocking lesion, whereas template switching uses a Rad51/ssDNA nucleofilament and the sister chromatid to bypass the lesion. Rad51 is loaded at this nucleofilament by two mediator proteins, BRCA2 and Rad52, and these three factors are critical for homologous recombination (HR). Here, we review recent advances showing that Rad51, BRCA2, and Rad52 perform some of these functions through mechanisms that do not require the strand exchange activity of Rad51: the formation and protection of reversed fork structures aimed to bypass blocking lesions, and the promotion of TLS. These findings point to the central HR proteins as potential molecular switches in the choice of the mechanism of DDT.

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