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)

Most positive strand RNA viruses infecting plants and animals encode proteins containing the so-called nucleotide binding motif (NTBM) (1) in their amino acid sequences (2). As suggested from the high level of sequence similarity of these viral proteins with the recently described superfamilies of helicase-like proteins (3-5), the NTBM-containing cylindrical inclusion (CI) protein from plum pox virus (PPV), which belongs to the potyvirus group of positive strand RNA viruses, is shown to be able to unwind RNA duplexes. This activity was found to be dependent on the hydrolysis of NTP to NDP and Pi, and thus it can be considered as an RNA helicase activity. In the in vitro assay used, the PPV CI protein was only able to unwind double strand RNA substrates with 3' single strand overhangs. This result indicates that the helicase activity of the PPV CI protein functions in the 3' to 5' direction (6). To our knowledge, this is the first report on a helicase activity associated with a protein encoded by an RNA virus.
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PMID:RNA helicase: a novel activity associated with a protein encoded by a positive strand RNA virus. 226 59

The ATR-X syndrome is an X-linked disorder comprising severe psychomotor retardation, characteristic facial features, genital abnormalities, and alpha-thalassemia. We have shown that ATR-X results from diverse mutations of XH2, a member of a subgroup of the helicase superfamily that includes proteins involved in a wide range of cellular functions, including DNA recombination and repair (RAD16, RAD54, and ERCC6) and regulation of transcription (SW12/SNF2, MOT1, and brahma). The complex ATR-X phenotype suggests that XH2, when mutated, down-regulates expression of several genes, including the alpha-globin genes, indicating that it could be a global transcriptional regulator. In addition to its role in the ATR-X syndrome, XH2 may be a good candidate for other forms of X-linked mental retardation mapping to Xq13.
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PMID:Mutations in a putative global transcriptional regulator cause X-linked mental retardation with alpha-thalassemia (ATR-X syndrome). 769 14

It was shown recently that mutations of the ATRX gene give rise to a severe, X-linked form of syndromal mental retardation associated with alpha thalassaemia (ATR-X syndrome). In this study, we have characterised the full-length cDNA and predicted structure of the ATRX protein. Comparative analysis shows that it is an entirely new member of the SNF2 subgroup of a superfamily of proteins with similar ATPase and helicase domains. ATRX probably acts as a regulator of gene expression. Definition of its genomic structure enabled us to identify four novel splicing defects by screening 52 affected individuals. Correlation between these and previously identified mutations with variations in the ATR-X phenotype provides insights into the pathophysiology of this disease and the normal role of the ATRX protein in vivo.
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PMID:ATRX encodes a novel member of the SNF2 family of proteins: mutations point to a common mechanism underlying the ATR-X syndrome. 896 41

We have previously reported the isolation of a gene from Xq13, coding for a putative regulator of transcription (XNP). It is a member of the helicase family, and has now been shown to be the gene involved in the X-linked alpha-thalassemia/mental retardation (ATR-X) syndrome. ATR-X mutations were only found in the 3'-part of the coding sequence, which includes the helicase domains. However, no ATR-X mutation has yet been found in one of the seven conserved helicase domains. In this paper, we report a mutation in XNP, segregating in a family presenting an "ATR-X' phenotype without alpha-thalassemia, that causes a proline to serine transition in the helicase II domain.
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PMID:A point mutation in the XNP gene, associated with an ATR-X phenotype without alpha-thalassemia. 904 63

Drosophila maleless (mle) is required for X chromosome dosage compensation and is essential for male viability. Maleless protein (MLE) is highly homologous to human RNA helicase A and the bovine counterpart of RNA helicase A, nuclear helicase II. In this report, we demonstrate that MLE protein, overexpressed and purified from Sf9 cells infected with recombinant baculovirus, possesses RNA/DNA helicase, adenosine triphosphatase (ATPase) and single-stranded (ss) RNA/ssDNA binding activities, properties identical to RNA helicase A. Using site-directed mutagenesis, we created a mutant of MLE (mle-GET) that contains a glutamic acid in place of lysine in the conserved ATP binding site A. In vitro biochemical analysis showed that this mutation abolished both NTPase and helicase activities of MLE but affected the ability of MLE to bind to ssRNA, ssDNA and guanosine triphosphate (GTP) less severely. In vivo, mle-GET protein could still localize to the male X chromosome coincidentally with the male-specific lethal-1 protein, MSL-1, but failed to complement mle1 mutant males. These results indicate that the NTPase/helicase activities are essential functions of MLE for dosage compensation, perhaps utilized for chromatin remodeling of X-linked genes.
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PMID:The NTPase/helicase activities of Drosophila maleless, an essential factor in dosage compensation. 918 14

A search of the Human Genome Sciences database of expressed sequence-tagged DNA fragments, for sequences containing homology to known yeast DNA recombination and repair genes, yielded a cDNA fragment with high homology to RAD54. Here we describe the complete cDNA sequence and the characterization of the genomic locus coding for the human homologue of the yeast RAD54 gene (hRAD54). The yeast RAD54 belongs to the RAD52 epistasis group and appears to be involved in both DNA recombination and repair. The hRAD54 gene maps to chromosome 1p32 in a region of frequent loss of heterozygosity in breast tumors and encodes a protein of M(r) 93,000 that displays 52% identity to the yeast RAD54 protein. The hRAD54 protein sequence additionally contains all seven of the consensus segments of a superfamily of proteins with presumed or proven DNA helicase activity. Mutations in genes with consensus helicase homology have been found in cancer-prone syndromes such as xeroderma pigmentosum and Bloom syndrome as well as Werner's syndrome, in which patients age prematurely, and the X-linked mental retardation with alpha-thalassemia syndrome, ATR-X. We have examined the hRAD54 gene in several breast tumors and breast tumor cell lines and, although the gene region appears to be deleted in several tumors, at present we have found no coding sequence mutations.
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PMID:Characterization of the human homologue of RAD54: a gene located on chromosome 1p32 at a region of high loss of heterozygosity in breast tumors. 919 13

The XNP/ATR-X gene is involved in several X-linked mental retardation phenotypes: the ATR-X syndrome, the Juberg-Marsidi syndrome, and some severe mental retardation phenotypes without alpha-thalassemia. Using a vectorette strategy, we have identified and sequenced the intron/exon boundaries of this gene. The gene is composed of 35 exons. It encodes a potential protein of 2492 amino acids. A search of the databases identified three zinc finger motifs within the 5' end of the gene. Expression analysis in different tissues indicated that an alternative splicing event that involves exon 6 is occurring. One of these alternatively spliced transcripts is predominantly expressed in embryonic tissues. These data led us to search for mutations in the 5' region in ATRX patients without other mutations in the 3' region. In one patient a mutation was found in which part of exon 7 was removed from the XNP transcript, as a result of a mutation creating a novel splice site that is substituted for the natural splice site. This new splicing event removed one zinc finger motif. This is the first example of a mutation in XNP within the 5' coding region. It suggests that mutations will be predominantly found in the helicase region as well as in the zinc finger regions and leads us to propose a large screening of additional patients.
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PMID:Determination of the genomic structure of the XNP/ATRX gene encoding a potential zinc finger helicase. 924 31

Mutations in the ATRX gene are associated with an X-linked mental retardation (XLMR) syndrome most often accompanied by alpha-thalassaemia (ATR-X syndrome). The ATRX gene encodes a predicted protein of 280 kDa featuring a PHD zinc finger motif and an ATPase/helicase domain of the SWI/SNF type; the vast majority of mutations in the ATRX gene fall within these two motifs. Although these domains are suggestive of a role for ATRX in transcriptional regulation by affecting chromatin structure and/or function, the precise cellular role of the ATRX protein remains undefined. Using indirect immunofluorescence and biochemical fractionation, we demonstrate that the ATRX protein has a punctate nuclear staining pattern and that it is tightly associated with the nuclear matrix at interphase. At the onset of M phase, the ATRX protein was associated mainly with condensed chromatin. The association of the ATRX protein with chromosomes at mitosis is concomitant with phosphorylation of the protein and its association with heterochromatin protein 1alpha (HP1alpha). The phosphorylation-dependent changes in localization between the nuclear matrix and condensed chromatin are consistent with a dual role for ATRX, possibly involving gene regulation at interphase and chromosomal segregation at mitosis.
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PMID:Cell cycle-dependent phosphorylation of the ATRX protein correlates with changes in nuclear matrix and chromatin association. 1069 77

X-linked alpha-thalassemia/mental retardation syndrome (ATR-X) is one of the many known X-linked mental retardation syndromes. Mutations in the ATR-X gene (ATRX) that encodes a putative global transcription factor have been identified in patients with ATR-X as well as those with other forms of X-linked mental retardation syndrome. To better understand the genetic basis of ATR-X, we investigated nine patients with the ATR-X phenotype from eight independent Japanese families for mutations in ATRX. We identified seven missense mutations, including six novel mutations, all of which were located either in the N-terminal region corresponding to the putative zinc finger domain (N179S, P190L, V194I, and R246C) or in the C-terminal region corresponding to the helicase domain (V1552F, L1645S, and Y1847C). R246C was found in two independent patients. Furthermore, we investigated the origin of the mutations in seven mothers. Five mothers were found to be carriers, and two were not, indicating de novo origin of the mutations. When we compared clinical manifestations with respective mutations, we could not find apparent phenotype-genotype correlation. Therefore, the putative zinc finger domain and the helicase domains may have similar functional significance for the function of ATRX.
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PMID:Molecular genetic study of japanese patients with X-linked alpha-thalassemia/mental retardation syndrome (ATR-X). 1099 12

RNA helicase A (RHA) is a member of an ATPase/DNA and RNA helicase family and is a homologue of Drosophila maleless protein (MLE), which regulates X-linked gene expression. RHA is also a component of holo-RNA polymerase II (Pol II) complexes and recruits Pol II to the CREB binding protein (CBP). The ATPase and/or helicase activity of RHA is required for CREB-dependent transcription. To further understand the role of RHA on gene expression, we have identified a 50-amino-acid transactivation domain that interacts with Pol II and termed it the minimal transactivation domain (MTAD). The protein sequence of this region contains six hydrophobic residues and is unique to RHA homologues and well conserved. A mutant with this region deleted from full-length RHA decreased transcriptional activity in CREB-dependent transcription. In addition, mutational analyses revealed that several tryptophan residues in MTAD are important for the interaction with Pol II and transactivation. These mutants had ATP binding and ATPase activities comparable to those of wild-type RHA. A mutant lacking ATP binding activity was still able to interact with Pol II. In CREB-dependent transcription, the transcriptional activity of each of these mutants was less than that of wild-type RHA. The activity of the double mutant lacking both functions was significantly lower than that of each mutant alone, and the double mutant had a dominant negative effect. These results suggest that RHA could independently regulate CREB-dependent transcription either through recruitment of Pol II or by ATP-dependent mechanisms.
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PMID:Dual roles of RNA helicase A in CREB-dependent transcription. 1141 26


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