scholarly journals Identification and Characterization of a Novel Recurrent ERCC6 Variant in Patients with a Severe Form of Cockayne Syndrome B

Genes ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1922
Author(s):  
Khouloud Zayoud ◽  
Ichraf Kraoua ◽  
Asma Chikhaoui ◽  
Nadège Calmels ◽  
Sami Bouchoucha ◽  
...  
Keyword(s):  
Excision Repair ◽  
Severe Form ◽  
Cockayne Syndrome ◽  
Homozygous Mutation ◽  
Clinical Genetic ◽  
Western Blots ◽  
Nucleotide Excision ◽  
Tunisian Patients ◽  
Functional Analyses

Cockayne syndrome (CS) is a rare disease caused by mutations in ERCC6/CSB or ERCC8/CSA. We report here the clinical, genetic, and functional analyses of three unrelated patients mutated in ERCC6/CSB with a severe phenotype. After clinical examination, two patients were investigated via next generation sequencing, targeting seventeen Nucleotide Excision Repair (NER) genes. All three patients harbored a novel, c.3156dup, homozygous mutation located in exon 18 of ERCC6/CSB that affects the C-terminal region of the protein. Sanger sequencing confirmed the mutation and the parental segregation in the three families, and Western blots showed a lack of the full-length protein. NER functional impairment was shown by reduced recovery of RNA synthesis with proficient unscheduled DNA synthesis after UV-C radiations in patient-derived fibroblasts. Despite sharing the same mutation, the clinical spectrum was heterogeneous among the three patients, and only two patients displayed clinical photosensitivity. This novel ERCC6 variant in Tunisian patients suggests a founder effect and has implications for setting-up prenatal diagnosis/genetic counselling in North Africa, where this disease is largely undiagnosed. This study reveals one of the rare cases of CS clinical heterogeneity despite the same mutation. Moreover, the occurrence of an identical homozygous mutation, which either results in clinical photosensitivity or does not, strongly suggests that this classic CS symptom relies on multiple factors.

scholarly journals Structural studies on M. tuberculosis O6-methylguanine methyltransferase

2014 ◽  
Vol 70 (a1) ◽  
pp. C832-C832
Author(s):  
Menico Rizzi ◽  
Riccardo Miggiano ◽  
Samarpita Lahiri ◽  
Giuseppe Perugino ◽  
Maria Ciaramella ◽  
...  
Keyword(s):  
Excision Repair ◽  
Single Step ◽  
Double Stranded Dna ◽  
Nucleotide Excision ◽  
Enzymatic Systems ◽  
Methylguanine Methyltransferase ◽  
Mutagenic Effects ◽  
Wild Type Form

Mycobacterium tuberculosis (MTB) is an extremely well adapted human pathogen capable to survive for decades inside the hostile environment represented by the host's infected macrophages despite exposure to multiple potential DNA-damaging stresses. In order to maintain a remarkable low level of genetic diversity, MTB deploys different strategies of DNA repair, including multi-enzymatic systems, such as Nucleotide Excision Repair, and single-step repair. In particular, to counteract the mutagenic effects of DNA alkylation, MTB performs the direct alkylated-base reversal by sacrificing one molecule of a DNA-protein alkyltransferase, such as O6-methylguanine methyltransferase (OGT; orf: Rv1316c). We present here the biochemical and structural characterization of recombinant mycobacterial OGT (MtOGT) in its wild-type form along with its mutated variants mimicking the ones occurring in relevant clinical strains (i.e. MtOGT-T15S and MtOGT-R37L). Our studies reveal that MtOGT-R37L is severely impaired in its activity as consequence of its ten-fold lower affinity for modified double-stranded DNA (dsDNA) (1). Further investigations on a new structure-based panel of OGT versions, designed to explore different molecular environment at position 37, allowed us a better understanding of the functional role of the MtOGT Arg37-bearing loop during catalysis. Moreover, we solved the crystal structure of MtOGT in covalent complex with modified dsDNA that reveals an unprecedented MtOGT::DNA architecture, suggesting that the MtOGT monomer performing the catalysis needs assisting unreacted subunits during cooperative DNA binding. This work is supported by European Community FP7 program SYSTEMTB (Health-F4-2010-241587)

scholarly journals A Ubiquitin-Binding Domain in Cockayne Syndrome B Required for Transcription-Coupled Nucleotide Excision Repair

2010 ◽  
Vol 38 (5) ◽  
pp. 637-648 ◽  
Author(s):  
Roy Anindya ◽  
Pierre-Olivier Mari ◽  
Ulrik Kristensen ◽  
Hanneke Kool ◽  
Giuseppina Giglia-Mari ◽  
...  
Keyword(s):  
Nucleotide Excision Repair ◽  
Excision Repair ◽  
Cockayne Syndrome ◽  
Binding Domain ◽  
Nucleotide Excision ◽  
Ubiquitin Binding ◽  
Ubiquitin Binding Domain

scholarly journals Heterogeneous clinical features in Cockayne syndrome-A patients with the same mutation and in siblings

2021 ◽  
Author(s):  
Asma CHIKHAOUI ◽  
Ichraf Kraoua ◽  
Nadège Calmels ◽  
Sami Bouchoucha ◽  
Cathy Obringer ◽  
...  
Keyword(s):  
North Africa ◽  
Clinical Symptoms ◽  
Excision Repair ◽  
Functional Characterization ◽  
Clinical Manifestations ◽  
Case Series ◽  
Cockayne Syndrome ◽  
The Other ◽  
Indel Mutation

Abstract Background Cockayne syndrome (CS) is a rare autosomal recessive disorder caused by mutations in ERCC6/CSB or ERCC8/CSA that participate in transcription-coupled nucleotide excision repair (TC-NER) of UV-induced DNA damage. CS patients display a large heterogeneity of clinical symptoms and severities, the reason of which is not fully understood, and little data is available for affected siblings. CS is largely undiagnosed in North Africa. Methods We report here the clinical description as well as genetic and functional characterization of eight North African CS patients, including siblings. These patients, who belonged to six unrelated families, underwent complete clinical examination and biochemical analyses. Sanger sequencing was performed for the recurrent mutation in five families, and targeted gene sequencing for one patient of the other family. We also performed RRS (Recovery RNA Synthesis) to confirm the functional impairment of DNA repair in the identified mutations. Results Six out of eight patients carried a homozygous indel mutation (c.598_600delinsAA) in exon 7 of ERCC8, and displayed a variable clinical spectrum, including between siblings, despite sharing the same mutation. The other two patients were Tunisian siblings who carried a homozygous splice-site variant in ERCC8 (c.843 + 1 G > C). They presented more severe clinical manifestations, which are in general rarely associated with CSA mutations, leading to gastrostomy and hepatic damage. Impaired TC-NER was confirmed by RRS in six tested patients. Conclusions This study provides the first deep characterization of case series of rare CS-A patients in North Africa. They carry mutations described to date only in this region and the Middle-East. We also provide the largest characterization of unrelated patients, as well as siblings, with the same mutation, providing a framework for dissecting elusive genotype-phenotype correlations in CS.

scholarly journals Genome-wide role of Rad26 in promoting transcription-coupled nucleotide excision repair in yeast chromatin

2020 ◽  
Vol 117 (31) ◽  
pp. 18608-18616 ◽  
Author(s):  
Mingrui Duan ◽  
Kathiresan Selvam ◽  
John J. Wyrick ◽  
Peng Mao
Keyword(s):  
Nucleotide Excision Repair ◽  
Transcription Initiation ◽  
Excision Repair ◽  
Elongation Factor ◽  
Cockayne Syndrome ◽  
Proximal Half ◽  
Genome Wide ◽  
Nucleotide Excision ◽  
Nucleotide Resolution

Transcription-coupled nucleotide excision repair (TC-NER) is an important DNA repair mechanism that removes RNA polymerase (RNAP)-stalling DNA damage from the transcribed strand (TS) of active genes. TC-NER deficiency in humans is associated with the severe neurological disorder Cockayne syndrome. Initiation of TC-NER is mediated by specific factors such as the human Cockayne syndrome group B (CSB) protein or its yeast homolog Rad26. However, the genome-wide role of CSB/Rad26 in TC-NER, particularly in the context of the chromatin organization, is unclear. Here, we used single-nucleotide resolution UV damage mapping data to show that Rad26 and its ATPase activity is critical for TC-NER downstream of the first (+1) nucleosome in gene coding regions. However, TC-NER on the transcription start site (TSS)-proximal half of the +1 nucleosome is largely independent of Rad26, likely due to high occupancy of the transcription initiation/repair factor TFIIH in this nucleosome. Downstream of the +1 nucleosome, the combination of low TFIIH occupancy and high occupancy of the transcription elongation factor Spt4/Spt5 suppresses TC-NER in Rad26-deficient cells. We show that deletion ofSPT4significantly restores TC-NER across the genome in arad26∆mutant, particularly in the downstream nucleosomes. These data demonstrate that the requirement for Rad26 in TC-NER is modulated by the distribution of TFIIH and Spt4/Spt5 in transcribed chromatin and Rad26 mainly functions downstream of the +1 nucleosome to remove TC-NER suppression by Spt4/Spt5.

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