scholarly journals HIV-1 and HIV-2 exhibit divergent interactions with HLTF and UNG2 DNA repair proteins

2016 ◽  
Vol 113 (27) ◽  
pp. E3921-E3930 ◽  
Author(s):  
Kasia Hrecka ◽  
Caili Hao ◽  
Ming-Chieh Shun ◽  
Sarabpreet Kaur ◽  
Selene K. Swanson ◽  
...  
Keyword(s):  
Dna Repair ◽  
Excision Repair ◽  
Host Cells ◽  
Hiv Replication ◽  
Dna Repair Enzymes ◽  
Repair Enzymes ◽  
Dna Repair Proteins ◽  
Base Excision ◽  
High Concentrations ◽  
Hiv 1

HIV replication in nondividing host cells occurs in the presence of high concentrations of noncanonical dUTP, apolipoprotein B mRNA-editing, enzyme-catalytic, polypeptide-like 3 (APOBEC3) cytidine deaminases, and SAMHD1 (a cell cycle-regulated dNTP triphosphohydrolase) dNTPase, which maintains low concentrations of canonical dNTPs in these cells. These conditions favor the introduction of marks of DNA damage into viral cDNA, and thereby prime it for processing by DNA repair enzymes. Accessory protein Vpr, found in all primate lentiviruses, and its HIV-2/simian immunodeficiency virus (SIV) SIVsm paralogue Vpx, hijack the CRL4DCAF1E3 ubiquitin ligase to alleviate some of these conditions, but the extent of their interactions with DNA repair proteins has not been thoroughly characterized. Here, we identify HLTF, a postreplication DNA repair helicase, as a common target of HIV-1/SIVcpz Vpr proteins. We show that HIV-1 Vpr reprograms CRL4DCAF1E3 to direct HLTF for proteasome-dependent degradation independent from previously reported Vpr interactions with base excision repair enzyme uracil DNA glycosylase (UNG2) and crossover junction endonuclease MUS81, which Vpr also directs for degradation via CRL4DCAF1E3. Thus, separate functions of HIV-1 Vpr usurp CRL4DCAF1E3 to remove key enzymes in three DNA repair pathways. In contrast, we find that HIV-2 Vpr is unable to efficiently program HLTF or UNG2 for degradation. Our findings reveal complex interactions between HIV-1 and the DNA repair machinery, suggesting that DNA repair plays important roles in the HIV-1 life cycle. The divergent interactions of HIV-1 and HIV-2 with DNA repair enzymes and SAMHD1 imply that these viruses use different strategies to guard their genomes and facilitate their replication in the host.

scholarly journals New perspectives in cancer biology from a study of canonical and non-canonical functions of base excision repair proteins with a focus on early steps

Mutagenesis ◽  
2019 ◽  
Vol 35 (1) ◽  
pp. 129-149 ◽  
Author(s):  
Matilde Clarissa Malfatti ◽  
Giulia Antoniali ◽  
Marta Codrich ◽  
Silvia Burra ◽  
Giovanna Mangiapane ◽  
...  
Keyword(s):  
Dna Repair ◽  
Base Excision Repair ◽  
Cancer Biology ◽  
Molecular Mechanisms ◽  
Excision Repair ◽  
Dna Lesions ◽  
Cancer Development ◽  
Dna Repair Enzymes ◽  
Repair Enzymes ◽  
Base Excision

Abstract Alterations of DNA repair enzymes and consequential triggering of aberrant DNA damage response (DDR) pathways are thought to play a pivotal role in genomic instabilities associated with cancer development, and are further thought to be important predictive biomarkers for therapy using the synthetic lethality paradigm. However, novel unpredicted perspectives are emerging from the identification of several non-canonical roles of DNA repair enzymes, particularly in gene expression regulation, by different molecular mechanisms, such as (i) non-coding RNA regulation of tumour suppressors, (ii) epigenetic and transcriptional regulation of genes involved in genotoxic responses and (iii) paracrine effects of secreted DNA repair enzymes triggering the cell senescence phenotype. The base excision repair (BER) pathway, canonically involved in the repair of non-distorting DNA lesions generated by oxidative stress, ionising radiation, alkylation damage and spontaneous or enzymatic deamination of nucleotide bases, represents a paradigm for the multifaceted roles of complex DDR in human cells. This review will focus on what is known about the canonical and non-canonical functions of BER enzymes related to cancer development, highlighting novel opportunities to understand the biology of cancer and representing future perspectives for designing new anticancer strategies. We will specifically focus on APE1 as an example of a pleiotropic and multifunctional BER protein.

scholarly journals HIV-1 Vpr degrades the HLTF DNA translocase in T cells and macrophages

2016 ◽  
Vol 113 (19) ◽  
pp. 5311-5316 ◽  
Author(s):  
Hichem Lahouassa ◽  
Marie-Lise Blondot ◽  
Lise Chauveau ◽  
Ghina Chougui ◽  
Marina Morel ◽  
...  
Keyword(s):  
Dna Repair ◽  
Excision Repair ◽  
Host Cells ◽  
Uracil Dna Glycosylase ◽  
Proteomic Screen ◽  
Cycle Arrest ◽  
Immunodeficiency Virus ◽  
Base Excision ◽  
Hiv 1 ◽  
Dna Translocase

Viruses often interfere with the DNA damage response to better replicate in their hosts. The human immunodeficiency virus 1 (HIV-1) viral protein R (Vpr) protein has been reported to modulate the activity of the DNA repair structure-specific endonuclease subunit (SLX4) complex and to promote cell cycle arrest. Vpr also interferes with the base-excision repair pathway by antagonizing the uracil DNA glycosylase (Ung2) enzyme. Using an unbiased quantitative proteomic screen, we report that Vpr down-regulates helicase-like transcription factor (HLTF), a DNA translocase involved in the repair of damaged replication forks. Vpr subverts the DDB1–cullin4-associated-factor 1 (DCAF1) adaptor of the Cul4A ubiquitin ligase to trigger proteasomal degradation of HLTF. This event takes place rapidly after Vpr delivery to cells, before and independently of Vpr-mediated G2 arrest. HLTF is degraded in lymphocytic cells and macrophages infected with Vpr-expressing HIV-1. Our results reveal a previously unidentified strategy for HIV-1 to antagonize DNA repair in host cells.

scholarly journals Formation of cytosine glycol and 5,6-dihydroxycytosine in deoxyribonucleic acid on treatment with osmium tetroxide

1986 ◽  
Vol 235 (2) ◽  
pp. 531-536 ◽  
Author(s):  
M Dizdaroglu ◽  
E Holwitt ◽  
M P Hagan ◽  
W F Blakely
Keyword(s):  
Dna Repair ◽  
Formic Acid ◽  
Excision Repair ◽  
Dna Lesions ◽  
Gas Chromatography Mass Spectrometry ◽  
Dna Glycosylases ◽  
Thymine Glycol ◽  
Repair Enzymes ◽  
Base Excision

OsO4 selectively forms thymine glycol lesions in DNA. In the past, OsO4-treated DNA has been used as a substrate in studies of DNA repair utilizing base-excision repair enzymes such as DNA glycosylases. There is, however, no information available on the chemical identity of other OsO4-induced base lesions in DNA. A complete knowledge of such DNA lesions may be of importance for repair studies. Using a methodology developed recently for characterization of oxidative base damage in DNA, we provide evidence for the formation of cytosine glycol and 5,6-dihydroxycytosine moieties, in addition to thymine glycol, in DNA on treatment with OsO4. For this purpose, samples of OsO4-treated DNA were hydrolysed with formic acid, then trimethylsilylated and analysed by capillary gas chromatography-mass spectrometry. In addition to thymine glycol, 5-hydroxyuracil (isobarbituric acid), 5-hydroxycytosine and 5,6-dihydroxyuracil (isodialuric acid or dialuric acid) were identified in OsO4-treated DNA. It is suggested that 5-hydroxyuracil was formed by formic acid-induced deamination and dehydration of cytosine glycol, which was the actual oxidation product of the cytosine moiety in DNA. 5-Hydroxycytosine obviously resulted from dehydration of cytosine glycol, and 5,6-dihydroxyuracil from deamination of 5,6-dihydroxycytosine. This scheme was supported by the presence of 5-hydroxyuracil, uracil glycol and 5,6-dihydroxyuracil in OsO4-treated cytosine. Treatment of OsO4-treated cytosine with formic acid caused the complete conversion of uracil glycol into 5-hydroxyuracil. The implications of these findings relative to studies of DNA repair are discussed.

scholarly journals HIV-1 Vpr Reprograms CLR4DCAF1E3 Ubiquitin Ligase to Antagonize Exonuclease 1-Mediated Restriction of HIV-1 Infection

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Junpeng Yan ◽  
Ming-Chieh Shun ◽  
Caili Hao ◽  
Yi Zhang ◽  
Juan Qian ◽  
...  
Keyword(s):  
T Cells ◽  
Dna Repair ◽  
Accessory Protein ◽  
Dna Repair Enzymes ◽  
New Class ◽  
Repair Enzymes ◽  
Immunodeficiency Virus ◽  
Exonuclease 1 ◽  
Cellular Dna ◽  
Hiv 1

ABSTRACTViral accessory proteins hijack host cell E3 ubiquitin ligases to antagonize innate/intrinsic defenses and thereby provide a more permissive environment for virus replication. Human immunodeficiency virus type 1 (HIV-1) accessory protein Vpr reprograms CRL4DCAF1E3 to antagonize select postreplication DNA repair enzymes, but the significance and role of these Vpr interactions are poorly understood. To gain additional insights, we performed a focused screen for substrates of CRL4DCAF1E3 reprogrammed by HIV-1 Vpr among known postreplication DNA repair proteins and identified exonuclease 1 (Exo1) as a novel direct HIV-1 Vpr target. We show that HIV-1 Vpr recruits Exo1 to the CRL4DCAF1E3 complex for ubiquitination and subsequent proteasome-dependent degradation and that Exo1 levels are depleted in HIV-1-infected cells in a Vpr-dependent manner. We also show that Exo1 inhibits HIV-1 replication in T cells. Notably, the antagonism of Exo1 is a conserved function of main group HIV-1 and its ancestor Vpr proteins in the simian immunodeficiency virus from chimpanzee (SIVcpz) lineage, further underscoring the relevance of our findings. Overall, our studies (i) reveal that HIV-1 Vpr extensively remodels the cellular postreplication DNA repair machinery by impinging on multiple repair pathways, (ii) support a model in which Vpr promotes HIV-1 replication by antagonizing select DNA repair enzymes, and (iii) highlight the importance of a new class of restrictions placed on HIV-1 replication in T cells by the cellular DNA repair machinery.IMPORTANCEHIV-1 polymerase reverse transcribes the viral RNA genome into imperfectly double-stranded proviral DNA, containing gaps and flaps, for integration into the host cell chromosome. HIV-1 reverse transcripts share characteristics with cellular DNA replication intermediates and are thought to be converted into fully double-stranded DNA by cellular postreplication DNA repair enzymes. Therefore, the finding that the HIV-1 accessory protein Vpr antagonizes select postreplication DNA repair enzymes that can process HIV-1 reverse transcripts has been surprising. Here, we show that one such Vpr-antagonized enzyme, exonuclease 1, inhibits HIV-1 replication in T cells. We identify exonuclease 1 as a member of a new class of HIV-1 restriction factors in T cells and propose that certain modes of DNA “repair” inhibit HIV-1 infection.

scholarly journals Inhibition of DNA repair glycosylases by base analogs and tryptophan pyrolysate, Trp-P-1.

2005 ◽  
Vol 52 (1) ◽  
pp. 167-178 ◽  
Author(s):  
Elzbieta Speina ◽  
Jarosław M Cieśla ◽  
Maria-Anna Graziewicz ◽  
Jacques Laval ◽  
Zygmunt Kazimierczuk ◽  
...  
Keyword(s):  
Dna Repair ◽  
Excision Repair ◽  
Dna Structure ◽  
Dna Glycosylases ◽  
Ap Endonuclease ◽  
Abasic Sites ◽  
Repair Enzymes ◽  
Lyase Activity ◽  
Base Analog ◽  
Base Excision

DNA base analogs, 2,4,5,6-substituted pyrimidines and 2,6-substituted purines were tested as potential inhibitors of E. coli Fpg protein (formamidopyrimidine -DNA glycosylase). Three of the seventeen compounds tested revealed inhibitory properties. 2-Thioxanthine was the most efficient, inhibiting 50% of 2,6-diamino-4-hydroxy-5N-methyl-formamidopyrimidine (Fapy-7MeG) excision activity at 17.1 microM concentration. The measured K(i) was 4.44 +/- 0.15 microM. Inhibition was observed only when the Fpg protein was first challenged to its substrate followed by the addition of the base analog, suggesting uncompetitive (catalytic) inhibition. For two other compounds, 2-thio- or 2-oxo-4,5,6-substituted pyrimidines, IC(50) was only 343.3 +/- 58.6 and 350 +/- 24.4 microM, respectively. No change of the Fpg glycosylase activity was detected in the presence of Fapy-7MeG, up to 5 microM. We also investigated the effect of DNA structure modified by tryptophan pyrolysate (Trp-P-1) on the activity of base excision repair enzymes: Escherichia coli and human DNA glycosylases of oxidized (Fpg, Nth) and alkylated bases (TagA, AlkA, and ANPG), and for bacterial AP endonuclease (Xth protein). Trp-P-1, which changes the secondary DNA structure into non-B, non-Z most efficiently inhibited excision of alkylated bases by the AlkA glycosylase (IC(50) = 1 microM). The ANPG, TagA, and Fpg proteins were also inhibited although to a lesser extent (IC(50) = 76.5 microM, 96 microM, and 187.5 microM, respectively). Trp-P-1 also inhibited incision of DNA at abasic sites by the beta-lyase activity of the Fpg and Nth proteins, and to a lesser extent by the Xth AP endonuclease. Thus, DNA conformation is critical for excision of damaged bases and incision of abasic sites by DNA repair enzymes.

scholarly journals Beyond Base Excision Repair: An evolving picture of mitochondrial DNA repair

2021 ◽  
Author(s):  
Kathrin Allkanjari ◽  
Robert A Baldock
Keyword(s):  
Dna Repair ◽  
Mitochondrial Dna ◽  
Mitochondrial Genome ◽  
Base Excision Repair ◽  
Excision Repair ◽  
Cellular Aging ◽  
Cellular Respiration ◽  
Dna Repair Proteins ◽  
Repair Mechanisms ◽  
Base Excision

Mitochondria are highly specialised organelles required for cellular processes including ATP-production through cellular respiration and controlling apoptosis. Mitochondria contain their own DNA genome which encodes both protein and RNA required for cellular respiration. Each cell may contain hundreds to thousands of copies of the mitochondrial genome, which is essential for normal cellular function – deviation of mitochondrial DNA (mtDNA) copy number is associated with cellular aging and disease. Furthermore, mtDNA lesions can arise from both endogenous or exogenous sources and must either be tolerated or corrected to preserve mitochondrial function. Importantly, replication of damaged mtDNA can lead to stalling and introduction of mutations or genetic loss, mitochondria have adapted mechanisms to repair damaged DNA. These mechanisms rely on nuclear encoded DNA repair proteins that are translocated into the mitochondria. Despite the presence of many known nuclear DNA repair proteins being found in the mitochondrial proteome, it remains to be established which DNA repair mechanisms are functional in mammalian mitochondria. Here, we summarise the existing and emerging research, alongside examining proteomic evidence, demonstrating that mtDNA damage can be repaired using Base Excision Repair (BER), Homologous Recombination (HR) and Microhomology-mediated End Joining (MMEJ). Critically, these repair mechanisms do not operate in isolation and evidence for interplay between pathways and repair associated with replication is discussed. Importantly, characterising non-canonical functions of key proteins and understanding the bespoke pathways used to tolerate, repair or bypass DNA damage will be fundamental in fully understanding the causes of mitochondrial genome mutations and mitochondrial dysfunction.

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