Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q00604 (X-linked)
 16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The X-linked form of the human disease dyskeratosis congenita (DKC) is caused by mutations in the gene encoding dyskerin. Sufferers have defects in highly regenerative tissues such as skin and bone marrow, chromosome instability and a predisposition to develop certain types of malignancy. Dyskerin is a putative pseudouridine synthase, and it has been suggested that DKC may be caused by a defect in ribosomal RNA processing. Here we show that dyskerin is associated not only with H/ACA small nucleolar RNAs, but also with human telomerase RNA, which contains an H/ACA RNA motif. Telomerase adds simple sequence repeats to chromosome ends using an internal region of its RNA as a template, and is required for the indefinite proliferation of primary human cells. We find that primary fibroblasts and lymphoblasts from DKC-affected males are not detectably deficient in conventional H/ACA small nucleolar RNA accumulation or function; however, DKC cells have a lower level of telomerase RNA, produce lower levels of telomerase activity and have shorter telomeres than matched normal cells. The pathology of DKC is consistent with compromised telomerase function leading to a defect in telomere maintenance, which may limit the proliferative capacity of human somatic cells in epithelia and blood.
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PMID:A telomerase component is defective in the human disease dyskeratosis congenita. 1059 Dec 18

Dyskeratosis congenita (DC) is characterised by the failure of those tissues that are rapidly dividing in the adult, particularly the skin and haemopoietic system. The X-linked form of the disease is caused by mutations in the DKC1 gene. To date the only DKC1 mutations detected result in alterations in the amino acid sequence of dyskerin. Dyskerin is the catalytic subunit of the H+ACA box small nucleolar RNA particles responsible for the site-specific pseudouridination of rRNA and in humans is also a component of the telomerase complex. In order to further characterise the disease at the molecular level, male DC patients from 25 families were screened for mutations in the DKC1 gene. Sequence variations were detected in 10 of these families. In five families, previously identified mutations were detected. Of the five novel sequence changes, three were coding changes: R158 W, S280R and P384L. A fourth sequence change was detected in the 5'-flanking region that disrupts a putative Spl transcription factor binding site. An intronic change was also detected that resulted in the partial incorporation of a portion of intron 1 into the mRNA. The identification of this mutation highlights the importance of screening for mutations that cause the partial aberrant splicing of mRNA. This is the first report of DKC1 mutations that are predicted to affect the level of expression of dyskerin. This suggests that a decrease in the amount of the normal protein may cause the disease.
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PMID:Identification of novel DKC1 mutations in patients with dyskeratosis congenita: implications for pathophysiology and diagnosis. 1137 75

Dyskeratosis congenita is a progressive bone-marrow failure syndrome that is characterized by abnormal skin pigmentation, leukoplakia and nail dystrophy. X-linked, autosomal recessive and autosomal dominant inheritance have been found in different pedigrees. The X-linked form of the disease is due to mutations in the gene DKC1 in band 2, sub-band 8 of the long arm of the X chromosome (ref. 3). The affected protein, dyskerin, is a nucleolar protein that is found associated with the H/ACA class of small nucleolar RNAs and is involved in pseudo-uridylation of specific residues of ribosomal RNA. Dyskerin is also associated with telomerase RNA (hTR), which contains a H/ACA consensus sequence. Here we map the gene responsible for dyskeratosis congenita in a large pedigree with autosomal dominant inheritance. Affected members of this family have an 821-base-pair deletion on chromosome 3q that removes the 3' 74 bases of hTR. Mutations in hTR were found in two other families with autosomal dominant dyskeratosis congenita.
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PMID:The RNA component of telomerase is mutated in autosomal dominant dyskeratosis congenita. 1157 67

Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome exhibiting considerable clinical and genetic heterogeneity. X-linked recessive, autosomal dominant and autosomal recessive forms are recognised. The gene mutated in X-linked DC (DKC1) encodes a highly conserved nucleolar protein called dyskerin. Dyskerin associates with the H/ACA class of small nucleolar RNAs which are important in guiding the conversion of uracil to pseudouracil in ribosomal RNA. Dyskerin also associates with the RNA component of telomerase (hTR) which is important in the maintenance of telomeres. Mutations in hTR were recently demonstrated in patients with autosomal dominant DC and in a subset of patients with aplastic anaemia (AA) but without other diagnostic features of DC. This discovery demonstrates that both DC and a subset of AA are due to a defect in telomerase. The link between DC and AA and in turn to defective telomerase suggests that treatments directed at correction of telomerase activity might benefit DC/AA patients who do not respond to conventional therapy.
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PMID:Dyskeratosis congenita: its link to telomerase and aplastic anaemia. 1455 76

Dyskerin is a nucleolar protein present in small nucleolar ribonucleoprotein particles that modify specific uridine residues of rRNA by converting them to pseudouridine. Dyskerin is also a component of the telomerase complex. Point mutations in the human gene encoding dyskerin cause the skin and bone marrow failure syndrome dyskeratosis congenita (DC). To test the extent to which disruption of pseudouridylation or telomerase activity may contribute to the pathogenesis of DC, we introduced two dyskerin mutations into murine embryonic stem cells. The A353V mutation is the most frequent mutation in patients with X-linked DC, whereas the G402E mutation was identified in a single family. The A353V, but not the G402E, mutation led to severe destabilization of telomerase RNA, a reduction in telomerase activity, and a significant continuous loss of telomere length with increasing numbers of cell divisions during in vitro culture. Both mutations caused a defect in overall pseudouridylation and a small but detectable decrease in the rate of pre-rRNA processing. In addition, both mutant embryonic stem cell lines showed a decrease in the accumulation of a subset of H/ACA small nucleolar RNAs, correlating with a significant decrease in site-specific pseudouridylation efficiency. Interestingly, the H/ACA snoRNAs decreased in the G402E mutant cell line differed from those affected in A353V mutant cells. Hence, our findings show that point mutations in dyskerin may affect both the telomerase and pseudouridylation pathways and the extent to which these functions are altered can vary for different mutations.
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PMID:Mouse dyskerin mutations affect accumulation of telomerase RNA and small nucleolar RNA, telomerase activity, and ribosomal RNA processing. 1524 Aug 72

Dyskeratosis congenita (DC) is a rare multi-system syndrome characterized by nail dystrophy, abnormal skin pigmentation and mucosal leukoplakia. The gene mutated in the X-linked form of human DC encodes for dyskerin, a nucleolar pseudourydilase that is involved in rRNA maturation. Dyskerin is also involved in telomerase function through its interaction with the telomerase RNA (hTR). Mutations in dyskerin result in low levels of hTR, decreased telomerase activity and telomere shortening. Autosomal dominant DC is characterized by mutations in hTR, supporting the hypothesis that the DC phenotype may be caused by impaired telomere maintenance. Several mutations have been identified in different regions of hTR in patients affected by autosomal dominant DC. Recent reports have shown that coexpression of wild-type hTR with hTR harboring mutations found in the pseudoknot domain does not affect telomerase activity in vitro. However, these studies did not assess the consequences of mutant hTR expression at the telomeres. Here we provide the first direct in vivo evidence that a mutant hTR carrying the GC to AG double substitution in the pseudoknot at nucleotides 107-108 found in patients affected by autosomal dominant DC does not behave as a dominant-negative for telomere maintenance. Rather it reconstitutes a weakly active telomerase enzyme, which is defective in telomere elongation.
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PMID:Telomerase RNA mutated in autosomal dyskeratosis congenita reconstitutes a weakly active telomerase enzyme defective in telomere elongation. 1575 47

DC is a multisystem bone marrow failure syndrome exhibiting marked clinical and genetic heterogeneity. X-linked, autosomal dominant and autosomal recessive subtypes are recognized. The gene mutated in X-linked DC (DKC1) encodes a highly conserved nucleolar protein called dyskerin. Dyskerin associates with the H/ACA motif class of small nucleolar RNAs in small nucleolar ribonucleoprotein particles that are important in guiding the conversion of uracil to pseudouracil during the maturation of ribosomal RNA. Dyskerin also associates with the TERC, which is important in the maintenance of telomeres. Mutations in TERC have been identified in patients with autosomal dominant DC and in a subset of patients with aplastic anemia and myelodysplasia. Recently, heterozygous mutations in TERT have been found in some patients with autosomal dominant DC and aplastic anemia. Additionally, patients with the severe multisystem disorder, Hoyeraal-Hreidarsson syndrome, have been found to have DKC1 mutations. Collectively, these observations have demonstrated that classical DC, Hoyeraal-Hreidarsson syndrome and a subset of aplastic anemia are due to a primary defect in telomerase. The critical role of telomeres and telomerase in humans is seen in the multisystem abnormalities found in these patients, including the increased incidence of malignancy. As bone marrow failure is the principal cause of death, conventional allografts have been attempted with limited success due to the high rate of pulmonary and endothelial complications. However, outcomes have improved with the use of non-myeloablative protocols, although the follow up is too short to evaluate long term toxicity and the natural course of the disease and it may be that correction of the telomerase defect is essential for the treatment of these patients.
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PMID:Dyskeratosis congenita: advances in the understanding of the telomerase defect and the role of stem cell transplantation. 1766 79

Dyskerin gene is mutated in patients with X-linked dyskeratosis congenita (X-DC), which results in greatly reduced levels of telomerase activity. A genetic suppressor element (GSE) termed GSE24-2 has been isolated in a screening for cisplatin resistance. GSE24-2-expressing cells presented impaired telomerase inhibition following in vitro exposure to chemotherapies, such as cisplatin, or telomerase inhibitors. The promoter of the telomerase component hTERT was constitutively activated in GSE24-2 cells in a c-myc expression-dependent manner. Deletion analyses and mutagenesis of the human c-myc promoter demonstrated that the target sequence for activation was the nuclease hypersensitive element-III (NHEIII) site located upstream to the P1 region of the promoter. Further, expression of GSE24-2 in cell lines derived from patients with X-DC and in VA13 cells induced increased hTERT RNA and hTR levels and recovery of telomerase activity. Finally, expression of GSE24-2 was able to rescue X-DC fibroblasts from premature senescence. These data demonstrate that this domain of dyskerin plays an important role in telomerase maintenance following cell insults such as cisplatin treatment, and in telomerase-defective cells in patients with X-DC. The expression of this dyskerin fragment has a dominant function in X-DC cells and could provide the basis for a therapeutic approach to this disease.
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PMID:A dyskerin motif reactivates telomerase activity in X-linked dyskeratosis congenita and in telomerase-deficient human cells. 1805 29

Mutations in the X-linked gene, DKC1, encoding dyskerin, cause dyskeratosis congenita by leading to decreased telomerase activity and causing short telomeres. Dyskerin is also a pseudouridine synthase that modifies nascent ribosomal and other RNAs and it is not known if this function is affected by the mutations. Here we show that newly synthesized ribosomal RNA, extracted from human and mouse cells with pathogenic mutations, shows anomalous mobility in agarose gels under certain denaturation conditions. The anomalously migrating RNA is turned over rapidly. Analysis of ribosomal RNA in these cells suggests the altered mobility is due to inefficient pseudouridylation.
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PMID:Anomalous electrophoretic migration of newly synthesized ribosomal RNAs and their precursors from cells with DKC1 mutations. 1972 12

It has been proposed that human telomerase RNA (hTR) interacts with dyskerin, prior to assembly of the telomerase holoenzyme. The direct interaction of dyskerin and hTR has not been demonstrated and is an experimentally challenging research problem because of difficulties in expressing and purifying dyskerin in quantities that are useful for biophysical analysis. By orthogonally labeling dyskerin and hTR, we have been able to employ single-molecule two-color coincidence detection (TCCD) to observe directly the formation of a dyskerin.hTR complex. By systematic deletion of hTR subdomains, we have gained insights into the RNA sites required for interaction with dyskerin. We then investigated mutated forms of hTR and dyskerin that are associated with dyskeratosis congenita (DC), on the basis of clinical genetics studies, for their effects on the dyskerin.hTR interaction. Dyskerin mutations associated with X-linked DC resulted in significant impairment of the dyskerin.hTR interaction, whereas mutations in hTR associated with autosomal dominant (AD) DC did not affect the interaction. We propose that disruption of the dyskerin.hTR interaction may contribute to X-linked DC.
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PMID:Single-molecule analysis of the human telomerase RNA.dyskerin interaction and the effect of dyskeratosis congenita mutations. 1983 19


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