Error-Prone Replication through UV Lesions by DNA Polymerase θ Protects against Skin Cancers

ABSTRACT The yeast RAD30-encoded DNA polymerase η (Polη) bypasses a cis-syn thymine-thymine dimer efficiently and accurately. Human DNA polymerase η functions similarly in the bypass of this lesion, and mutations in human Polη result in the cancer prone syndrome, the variant form of xeroderma pigmentosum. UV light, however, also elicits the formation ofcis-syn cyclobutane dimers and (6-4) photoproducts at 5′-CC-3′ and 5′-TC-3′ sites, and in both yeast and human DNA, UV-induced mutations occur primarily by 3′ C to T transitions. Genetic studies presented here reveal a role for yeast Polη in the error-free bypass of cyclobutane dimers and (6-4) photoproducts formed at CC and TC sites. Thus, by preventing UV mutagenesis at a wide spectrum of dipyrimidine sites, Polη plays a pivotal role in minimizing the incidence of sunlight-induced skin cancers in humans.

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Structure and mechanism of human PrimPol, a DNA polymerase with primase activity

Science Advances ◽

10.1126/sciadv.1601317 ◽

2016 ◽

Vol 2 (10) ◽

pp. e1601317 ◽

Cited By ~ 35

Author(s):

Olga Rechkoblit ◽

Yogesh K. Gupta ◽

Radhika Malik ◽

Kanagalaghatta R. Rajashankar ◽

Robert E. Johnson ◽

...

Keyword(s):

Dna Polymerase ◽

Dna Lesions ◽

Remarkable Feature ◽

Dna Primase ◽

Human Enzyme ◽

Active Site Cleft ◽

Deoxynucleoside Triphosphate ◽

Dna Template ◽

Uv Lesions ◽

Single Enzyme

PrimPol is a novel human enzyme that contains both DNA primase and DNA polymerase activities. We present the first structure of human PrimPol in ternary complex with a DNA template-primer and an incoming deoxynucleoside triphosphate (dNTP). The ability of PrimPol to function as a DNA primase stems from a simple but remarkable feature—almost complete lack of contacts to the DNA primer strand. This, in turn, allows two dNTPs to bind initiation and elongation sites on the enzyme for the formation of the first dinucleotide. PrimPol shows the ability to synthesize DNA opposite ultraviolet (UV) lesions; however, unexpectedly, the active-site cleft of the enzyme is constrained, which precludes the bypass of UV-induced DNA lesions by conventional translesion synthesis. Together, the structure addresses long-standing questions about how DNA primases actually initiate synthesis and how primase and polymerase activities combine in a single enzyme to carry out DNA synthesis.

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Translesion Synthesis by DNA Polymerase θ Protects from Skin Cancers

Cancer Discovery ◽

10.1158/2159-8290.cd-rw2019-025 ◽

2019 ◽

Vol 9 (4) ◽

pp. 463.1-463

Keyword(s):

Dna Polymerase ◽

Translesion Synthesis ◽

Skin Cancers

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Rev1 promotes replication through UV lesions in conjunction with DNA polymerases η, ι, and κ but not DNA polymerase ζ

Genes & Development ◽

10.1101/gad.272229.115 ◽

2015 ◽

Vol 29 (24) ◽

pp. 2588-2602 ◽

Cited By ~ 2

Author(s):

Jung-Hoon Yoon ◽

Jeseong Park ◽

Juan Conde ◽

Maki Wakamiya ◽

Louise Prakash ◽

...

Keyword(s):

Dna Polymerase ◽

Crucial Role ◽

Genome Stability ◽

Dna Polymerases ◽

Translesion Synthesis ◽

Dna Lesions ◽

Human Cells ◽

Uv Lesions ◽

Human And Mouse

Translesion synthesis (TLS) DNA polymerases (Pols) promote replication through DNA lesions; however, little is known about the protein factors that affect their function in human cells. In yeast, Rev1 plays a noncatalytic role as an indispensable component of Polζ, and Polζ together with Rev1 mediates a highly mutagenic mode of TLS. However, how Rev1 functions in TLS and mutagenesis in human cells has remained unclear. Here we determined the role of Rev1 in TLS opposite UV lesions in human and mouse fibroblasts and showed that Rev1 is indispensable for TLS mediated by Polη, Polι, and Polκ but is not required for TLS by Polζ. In contrast to its role in mutagenic TLS in yeast, Rev1 promotes predominantly error-free TLS opposite UV lesions in humans. The identification of Rev1 as an indispensable scaffolding component for Polη, Polι, and Polκ, which function in TLS in highly specialized ways opposite a diverse array of DNA lesions and act in a predominantly error-free manner, implicates a crucial role for Rev1 in the maintenance of genome stability in humans.

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Capacity of RecA protein to bind preferentially to UV lesions and inhibit the editing subunit (epsilon) of DNA polymerase III: a possible mechanism for SOS-induced targeted mutagenesis.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.83.3.619 ◽

1986 ◽

Vol 83 (3) ◽

pp. 619-623 ◽

Cited By ~ 61

Author(s):

C. Lu ◽

R. H. Scheuermann ◽

H. Echols

Keyword(s):

Dna Polymerase ◽

Reca Protein ◽

Targeted Mutagenesis ◽

Dna Polymerase Iii ◽

Polymerase Iii ◽

Uv Lesions

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Rad51 recombinase prevents Mre11 nuclease-dependent degradation and excessive PrimPol-mediated elongation of nascent DNA after UV irradiation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1508543112 ◽

2015 ◽

Vol 112 (48) ◽

pp. E6624-E6633 ◽

Cited By ~ 41

Author(s):

María Belén Vallerga ◽

Sabrina F. Mansilla ◽

María Belén Federico ◽

Agustina P. Bertolin ◽

Vanesa Gottifredi

Keyword(s):

Dna Polymerase ◽

Uv Irradiation ◽

Dna Polymerases ◽

Strand Break ◽

S Phase ◽

Exonuclease Activity ◽

Replication Forks ◽

Translesion Dna Synthesis ◽

Phase Progression ◽

Uv Lesions

After UV irradiation, DNA polymerases specialized in translesion DNA synthesis (TLS) aid DNA replication. However, it is unclear whether other mechanisms also facilitate the elongation of UV-damaged DNA. We wondered if Rad51 recombinase (Rad51), a factor that escorts replication forks, aids replication across UV lesions. We found that depletion of Rad51 impairs S-phase progression and increases cell death after UV irradiation. Interestingly, Rad51 and the TLS polymerase polη modulate the elongation of nascent DNA in different ways, suggesting that DNA elongation after UV irradiation does not exclusively rely on TLS events. In particular, Rad51 protects the DNA synthesized immediately before UV irradiation from degradation and avoids excessive elongation of nascent DNA after UV irradiation. In Rad51-depleted samples, the degradation of DNA was limited to the first minutes after UV irradiation and required the exonuclease activity of the double strand break repair nuclease (Mre11). The persistent dysregulation of nascent DNA elongation after Rad51 knockdown required Mre11, but not its exonuclease activity, and PrimPol, a DNA polymerase with primase activity. By showing a crucial contribution of Rad51 to the synthesis of nascent DNA, our results reveal an unanticipated complexity in the regulation of DNA elongation across UV-damaged templates.

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