Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043346 (xeroderma pigmentosum)
 2,924 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Six known or predicted helicases that are mutated in human syndromes are now recognized. These syndromes include xeroderma pigmentosum, Cockayne's syndrome, trichothiodystrophy, Bloom's syndrome, Werner's syndrome, and alpha-thalassemia mental retardation on the X chromosome. The clinical abnormalities in these syndromes cover a broad spectrum, pointing to different cellular processes of DNA manipulation that are defective in these syndromes.
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PMID:DNA helicases in inherited human disorders. 922 11

Most of the genes involved in the pathogenesis of the DNA replication and repair syndromes have now been cloned, and our understanding of the basis for the pleiotropic phenotype associated with many of these syndromes has rapidly and dramatically expanded. The elucidation of the specific interactions between proteins that comprise the transcription factor complex TFIIH raises the possibility that nucleotide excision repair, RNA polymerase II transcription, and cell cycle control are connected. Defects in the XPB, XPD, and XPG genes can result in three different syndromes, xeroderma pigmentosum, Cockayne syndrome, or trichothiodystrophy, depending on the specific mutation involved. The recent cloning of the genes involved in Bloom syndrome (BLM) and Werner syndrome (WRN) show that both are DNA and RNA helicases with homology to each other and to other DExH box helicases, yet the mechanism by which defects in these genes cause such different phenotypes is not yet understood. The ataxia-telangiectasia gene (ATM) is involved in a variety of signal transduction pathways that regulate the cellular response to normal proliferative stimuli as well as the response to DNA damage, and the disruption of these signal transduction pathways provides an explanation for ataxia-telangiectasia characteristics such as ionizing radiation sensitivity, immunodeficiency, and infertility. Although the first Fanconi anemia gene (FAC) was cloned over 5 years ago, and a second Fanconi anemia gene (FAA) was cloned in 1996, the biochemical function of Fanconi anemia proteins largely remains a mystery. The recent construction of mutant mouse strains for several of these diseases should help unlock the difficult puzzle of the pathogenesis of these syndromes.
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PMID:Disorders of DNA replication and repair. 942 94

Most gerontologists believe aging did not evolve, is accidental, and is unrelated to development. The opposite viewpoint is most likely correct. Genetic drift occurs in finite populations and leads to homozygosity in multiple-alleled traits. Episodic selection events will alter random drift towards homozygosity in alleles that increase fitness with respect to the selection event. Aging increases population turnover, which accelerates the benefit of genetic drift. This advantage of aging led to the evolution of aging systems (ASs). Periodic predation was the most prevalent episodic selection pressure in evolution. Effective defenses to predation that allow exceptionally long lifespans to evolve are shells, extreme intelligence, isolation, and flight. Without episodic predation, aging provides no advantage and aging systems will be deactivated to increase reproductive potential in unrestricted environments. The periodic advantage of aging led to the periodic evolution of aging systems. Newer aging systems co-opted and added to prior aging systems. Aging organisms should have one dominant, aging system that co-opts vestiges of earlier-evolved systems as well as vestiges of prior systems. In human evolution, aging systems chronologically emerged as follows: telomere shortening, mitochondrial aging, mutation accumulation, senescent gene expression (AS#4), targeted somatic tissue apoptotic-atrophy (AS#5), and female reproductive tissue apoptotic-atrophy (AS#6). During famine or drought, to avoid extinction, reproduction is curtailed and aging is slowed or somewhat reversed to postpone or reverse reproductive senescence. AS#4-AS#6 are gradual and reversible aging systems. The life-extending/rejuvenating effects of caloric restriction support the idea of aging reversibility. Development and aging are timed by the gradual loss of cytosine methylation in the genome. Methylated cytosines (5mC) inhibit gene transcription, and deoxyribonucleic acid (DNA) cleavage by restriction enzymes. Cleavage inhibition prevents apoptosis, which requires DNA fragmentation. Free radicals catalyze the demethylation of 5mC while antioxidants catalyze the remethylation of cytosine by altering the activity of DNA methyltransferases. Hormones act as either surrogate free radicals by stimulating the cyclic adenosine monophosphate (cAMP) pathway or as surrogate antioxidants through cyclic guanosine monophosphate (cGMP) pathway stimulation. Access to DNA containing 5mC inhibited developmental and aging genes and restriction sites is allowed by DNA helicase strand separation. Tightly wound DNA does not allow this access. The DNA helicase generates free radicals during strand separation; hormones either amplify or counteract this effect. Caloric restriction slows or reverses the aging process by increasing melatonin levels, which suppresses reproductive and free radical hormones, while increasing antioxidant hormone levels. Cell apoptosis during CR leads to somatic wasting and a release of DNA, which increases bioavailable cGMP. The rapid aging diseases of progeria, the three diseases: (xeroderma pigmentosum (XP), Cockayne syndrome(CS), and ataxia telangiectasia (AT)), and Werner's syndrome are related to or caused by defects in three separate DNA helicases. The rapid aging diseases caused by mitochondrial malfunctions mirror those seen in XP, CS, and AT. Comparing these diseases allows for assignment of the different symptoms of aging to their respective aging systems. Follicle-stimulating hormone (FSH) demethylates the genes of AS#4, luteinizing hormone (LH) of AS#5, and estrogen of AS#6 while cortisol may act cooperatively with FSH and LH, and 5-alpha dihydrotestosterone (DHT) with FSH in these role. The Werner's DNA helicase links timing of the age of puberty, menopause, and maximum lifespan in one mechanism. Telomerase is under hormonal control. Most cancers likely result from malfunctions in the programmed apoptosis of AS#5 and AS#6. The Hayflick limit is reached primarily through loss of cytosine methylation of genes that inhibit replication. Men suffer the diseases of AS#4 at a higher rate than women who suffer from AS#5 more often. Adult mammal cloning suggests aging-related cellular demethylation, and thus aging, is reversible. This theory suggests that the protective effect of smoking and ibuprofen for Alzheimer's disease is caused through LH suppression.
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PMID:The evolution of aging: a new approach to an old problem of biology. 979 99

The hRAD54 protein belongs to a superfamily of DNA helicases, and mutations in genes with DNA helicase function have been found to be responsible for cancer-prone syndromes (xeroderma pigmentosum, Bloom syndrome, Werner syndrome). hRAD54 thus could be a candidate modifier gene in tumors characterized by allelic imbalance at 1p32, the chromosome region in which this gene is located. Using a panel of 38 1p and five 1q markers, we therefore performed deletion-mapping analysis on a series of 35 oligodendrogliomas, which were also studied for mutations in the hRAD54 gene. Deletions of the short arm of chromosome 1 were evidenced in 26 tumors, mostly involving 1p36-1p13; all thus displayed loss of the 1p32 region. We used PCR/SSCP to examine all 18 exons of the hRAD54 gene for mutations in 25 tumors, but the mobility shifts detected corresponded to previously identified polymorphic changes: T-to-C transition at nucleotide 2865 (with no amino acid change) and at nucleotide 3008, at the 3' untranslated region. We conclude that hRAD54 gene alterations are not required for malignant transformation of oligodendrogliomas.
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PMID:hRAD54 gene and 1p high-resolution deletion-mapping analyses in oligodendrogliomas. 1064 Jan 46

Studying monogenic hereditary disorders that manifest age-related phenotypes in cells, tissues, and the total organism would be helpful for clarifying the mechanisms of aging. In this context, seven human disorders that manifest age-related phenotypes have been found to be caused by aberrations of five proteins with seven helicase motifs conserved in most of the helicases. These disorders are xeroderma pigmentosum, Cockayne syndrome, trichothiodystrophy, Bloom syndrome, Werner syndrome, X-linked alpha-thalassemia/mental retardation syndrome, and Juberg-Marsidi syndrome. A decline of probably pleiotropic and fundamental function of helicases in these disorders is, therefore, implied to underlie not only the various age-related phenotypes of the disorders but also the pleiotropic and universal nature of ordinary aging. Consistent with this implication, studies of these seven disorders suggest that their various age-related phenotypes are caused by aberrations in multiple processes, especially transcription. Furthermore, a few studies imply some association between aberration of the helicases and phenotypes in ordinary aging.
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PMID:Helicases and aging. 1089 38

DNA helicases are a highly conserved group of enzymes that unwind DNA. They function in all processes in which access to single-stranded DNA is required, including DNA replication, DNA repair and recombination, and transcription of RNA. Defects in helicases functioning in one or more of these processes can result in characteristic human genetic disorders in which genomic instability and predisposition to cancer are common features. So far, different helicase genes have been found mutated in six such disorders. Mutations in XPB and XPD can result in xeroderma pigmentosum, Cockayne syndrome, or trichothiodystrophy. Mutations in the RecQ-like genes BLM, WRN, and RECQL4 can result in Bloom syndrome, Werner syndrome, and Rothmund-Thomson syndrome, respectively. Because XPB and XPD function in both nucleotide excision repair and transcription initiation, the cellular phenotypes associated with a deficiency of each one of them include failure to repair mutagenic DNA lesions and defects in the recovery of RNA transcription after UV irradiation. The functions of the RecQ-like genes are unknown; however, a growing body of evidence points to a function in restarting DNA replication after the replication fork has become stalled. The genomic instability associated with mutations in the RecQ-like genes includes spontaneous chromosome instability and elevated mutation rates. Mouse models for nearly all of these entities have been developed, and these should help explain the widely different clinical features that are associated with helicase mutations.
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PMID:DNA helicases, genomic instability, and human genetic disease. 1170 36

Deoxyribonucleic acid (DNA) repair is a fundamental process designed to keep the integrity of genomic DNA that is continuously challenged by intrinsic or environmental induced alterations. Numerous genes involved in DNA repair have been cloned and are involved in different DNA repair pathways: base excision repair, nucleotide excision repair, mismatch repair, DNA recombination. Inherited conditions due to mutations in DNA repair genes include mainly: xeroderma pigmentosum, Cockayne syndrome, Trichothiodystrophy, Bloom syndrome, Rothmund-Thomson syndrome, and Werner syndrome. Minor to major ocular manifestations occur in these syndromes. For example, eyelid skin cancers in xeroderma pigmentosum and retinal dystrophy in Cockayne syndrome are major features of these syndromes. This review focuses on the DNA repair pathways, the general and ocular features of the related syndromes, the laboratory tests useful for diagnosis, and the general processes implied with DNA repair (ultraviolet sensitivity, carcinogenesis, apoptosis, oxydative stress, and premature aging).
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PMID:Ocular manifestations in the inherited DNA repair disorders. 1255 31

Proteins having DNA helicase activity play very important roles in many processes involving DNA workings such as replication, repair, and recombination. In this decade, many DNA helicase genes have been cloned as the causative genes of human recessive heredity diseases. These are the causative genes for Xeroderma pigmentosum (XPB and XPD), Cockayne syndrome (CSB), diffuse collagen disease (Ku80), alpha-thalassmia (ATR-X), Bloom syndrome (BLM), Werner syndrome (WRN) and Rothmund-Thomson syndrome (RTS). The yeast homologue genes of these human DNA helicase genes exist. S. cerevisiae RAD25/SSL2, RAD3, RAD26, YKU80/HDF2 and RAD54 are the homologue for XPB/ERCC3, XPD/ERCC2, CSB/ERCC6, Ku80/XRCC5 and ATR-X/HX2, respectively. E coli. recQ gene and S. cerevisiae SGS1 are the homologue for all BLM, WRN and RTS. A search of whole genome of S. cerevisiae revealed that SGS1 is the sole homologue of recQ in S. cerevisiae. Thus it seems likely that SGS1 is a functional homologue of one or several human RecQ family genes. Many basic or essential functions are well conserved in the cells from lower eukaryotic to higher mammalian. The functional analysis in yeast could make an useful insight for the human homologue. To clarify the functions of S. cerevisiae Sgs1 and to get an insight into the functions of Blm, Wrn and Rts, in this study, we analyzed the phenotype of sgs1 disruptant and in detail the cause of the poor sporulation phenotype of sgs1 disruptants in relation to meiotic processes including meiotic recombination. The poor sporulation of sgs1 disruptants was complemented with a mutated SGS1 gene encoding a protein lacking DNA helicase activity; however, the mutated gene could suppress neither the sensitivity of sgs1 disruptants to methyl methanesulfonate (MMS) and hydroxyurea nor the mitotic hyperrecombination phenotype of sgs1 disruptants. The N-terminal 1-45 amino acid region and 698-1195 amino acid region of Sgs1, which including helicase domain and C-terminal RecQ conserved region with helicase activity, were required for complementation of MMS sensitivity and suppression of hyperrecombination of sgs1 disruptants in mitotic growth. The 126-400 and 596-1195 amino acid regions of Sgs1 were required for complementation of poor sporulation and of reduced meiotic functions. These regions required for the mitotic or meiotic functions of Sgs1 were well overlapped with the interaction regions of Top3 and Top2. Some of these results might explain the mechanism of the symptom of RecQ-related syndromes.
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PMID:[Functional analysis of yeast homologue gene associated with human DNA helicase causative syndromes]. 1263 84

Recombination can result in genetic instability, and thus constitutes an important factor in the carcinogenic conversion of mammalian cells. Here we describe the occurrence of UV-stimulated recombination called enhanced recombination (EREC), measured with the use of Herpes Simplex Viruses type 1 mutants. In normal diploid human cells, EREC is induced by UV-C, mitomycin C and ENU, but not by X-ray or MMS. The kinetics of induction of EREC is similar to that of other SOS-like responses such as enhanced reactivation (ER) and enhanced mutagenesis (EM). In contrast to the latter responses, EREC is induced to higher levels and persists for longer periods in DNA repair deficient fibroblasts derived from xeroderma pigmentosum (XP), Cockayne syndrome (CS) and Trichothiodystrophy (TTD) patients. This observation indicates that EREC is a distinct SOS-like response. Apparently, the presence of unrepaired DNA lesions in the host genome is a strongly inducing signal for EREC. On the other hand, in cells derived from patients suffering from Bloom, Werner or Rothmund-Thomson syndrome (RTS) the EREC response is absent. These data indicate that determining EREC is a useful assay to investigate diploid human fibroblasts for abnormalities in UV-stimulated recombination.
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PMID:Abnormal kinetics of induction of UV-stimulated recombination in human DNA repair disorders. 1459 43

Defects of DNA repair underlie genetic syndromes. Chromosomal aberrations and mutations might cause specific inborn defects. There are several syndromes with characteristic clinical features, which appear to be caused by chromosome instability which is a consequence of DNA repair defects. This article describe syndromes where hereditary mutations are the reason of chromosomal instability and cause serious clinical results: ataxia-telangiectasia, Nijmegen breakage syndrome, Bloom syndrome, Fanconi's anemia, ICF syndrome, Roberts syndrome, dominantly inherited--PCD, Werner syndrome, xeroderma pigmentosum, Cockayne syndrome, trichothiodystrophy (TTD) and Rothmund-Thomson syndrome (RTS).
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PMID:[Chromosome instability syndromes]. 1687 67


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