Transcriptional changes in trichothiodystrophy cells

Abstract

Mutations in three of the genes encoding the XPB, XPD and TTDA components of transcription factor TFIIH can result in the clinical phenotype of trichothiodystrophy (TTD). Different mutations in XPB and XPD can instead cause xeroderma pigmentosum (XP). The completely different features of these disorders have been attributed to TTD being a transcription syndrome. In order to detect transcriptional differences between TTD and XP cells from the XP-D complementation group, we have compared gene expression profiles in cultured fibroblasts from normal, XP and TTD donors. Although we detected transcriptional differences between individual cell strains, using an algorithm of moderate stringency, we did not identify any genes whose epression was reproducibly different in proliferating fibroblasts from each type of donor.Following UV-irradiation, many genes were up-and down-regulated in all three cell types. The micro-array analysis indicated some apparent differences between the different donor types, but on more detailed inspection, these turned out to be false positives. We conclude that there are minimal differences in gene expression in proliferating fibroblasts from TTD, XP-D and normal donors.Dear Errol I enclose a manuscript entitled "Transcriptional changes in trichothiodystrophy cells" that we would like to be considered for publication in DNAR. This paper reports on a very careful study that we have carried out, using micro-arrays, to look for specific transcriptional differences between TTD fibroblasts and XP-D or normal fibroblasts, both in unirradiated and irradiated cells. We were not able to detect any differences that could be attributed to a TTD-specific genotype. En route our study highlights a number of potential pitfalls that need to be avoided when using such an approach. In particular using a single defective cell line and its corrected derivative might generate data that can be easily misinterpreted.We hope that the results in this paper will be of interest to readers of DNAR.Best regards. strains, using an algorithm of moderate stringency, we did not identify any genes whose expression was reproducibly different in proliferating fibroblasts from each type of donor. Following UV-irradiation, many genes were up-and down-regulated in all three cell types. The micro-array analysis indicated some apparent differences between the different donor types, but on more detailed inspection, these turned out to be false positives. We conclude that there are minimal differences in gene expression in proliferating fibroblasts from TTD, XP-D and normal donors.3

Transcriptional and post-transcriptional regulation of nucleotide excision repair genes in human cells

“…Mutations in core components of NER leads to the human disorders xeroderma pigmentosum and trichothiodystrophy [5] while defects in the factors responsible for TC-NER give rise to the Cockayne’s and UV-sensitive syndromes [6]. Polymorphisms in NER genes have been linked to reduced repair capacity and cancer predisposition [7].…”

On the traces of XPD: cell cycle matters - untangling the genotype-phenotype relationship of XPD mutations

“…The transcriptional profiles of cell lines isolated from TTD and XPD patients revealed alterations of only a relatively small subset of the transcriptome, including down- and up-regulated genes [62,63]. In addition, the XP- and TTD-type mutations analyzed in these studies affected transcription of the downregulated genes to a similar extent, indicating that the transcription defect is probably not a prerogative of TTD as previously believed.…”

“…In addition, the XP- and TTD-type mutations analyzed in these studies affected transcription of the downregulated genes to a similar extent, indicating that the transcription defect is probably not a prerogative of TTD as previously believed. Remarkably, a mutant cell line derived from a cancer-prone XP-CS patient presented a high number of overexpressed genes, mainly encoding proteins that are involved in the regulation of cell proliferation, differentiation and transformation [62]. Thus transcriptional alterations may also contribute to the increased susceptibility to carcinogenesis in XP and in the combined syndromes.…”

“…Results from these studies showed that XPD mutations found in TTD patients, but not those found in XP patients, strongly impaired the ability of a purified TFIIH complex to sustain transcription of the reporter [41]. However, this view is challenged by DNA microarray studies showing that TTD and XP mutations affect basal transcription to similar levels in human fibroblast cell lines [62,63]. Interestingly, although they were limited to few disease-related point mutations, these studies revealed distinct transcriptional signatures of UV-irradiated human TTD, XP and XP-CS cell lines with both up- and down-regulated genes.…”

Papel das proteínas XPD e DNA polimerase eta nas respostas de células humanas a danos no genoma

“…Entretanto, é importante lembrar que a via de NER é menos ativa em células terminalmente diferenciadas, como é o caso dos neurônios e astrócitos (Nouspikel, 2007;Yamamoto et al, 2007) , o que explicaria em parte a ausência de diferenças na expressão gênica de fibroblastos de pacientes XP e TTD (Offman et al, 2008); assim, é possível que muitas das diferenças importantes entre os pacientes XP, XP/CS e TTD não sejam detectadas através do estudo de fibroblastos.…”