Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An unusual large heterochromatic segment around the pericentromeric region of the X-chromosome is reported. In normal circumstances, the pericentromeric region of the X-chromosome is negative by the restriction endonuclease AluI/Giemsa technique. However, this unusual X-chromosome was found to have AluI resistant (positive) chromatin. The evolution of extra heterochromatin is a postzygotic event as substantiated by the presence of a normal cell line.
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PMID:Evolution of pericentromeric heterochromatin of human X chromosome. 145 65

T4-binding globulin (TBG) is a glycoprotein of hepatic origin which transports thyroid hormone in serum. Inherited TBG defects in man are X-chromosome linked and are expressed in hemizygotes as complete deficiency, partial deficiency, or excess. Since TBG is not necessary for thyroid hormone action, affected subjects are healthy. Using DNA probes for human TBG, we searched for restriction fragment length polymorphisms in six affected males belonging to 6 unrelated families with inherited complete TBG deficiency and an equal number of normal males. TBG could not be detected in the serum of any of the TBG-deficient males by a specific and sensitive RIA capable of detecting as little as 5 micrograms TBG/L or 0.031% of the average normal serum TBG concentration. DNA isolated from white blood cells was digested with 11 restriction endonucleases, and the digests were submitted to DNA blot analysis using two cloned TBG-DNA probes which together covered the entire protein coding and the 5'-flanking sequences of the TBG gene. A total of 26 different bands were detected on DNA blots, identifying 18 restriction sites located within the 4.2-kilobase TBG gene, which includes intronic, exonic, and 5'-flanking sequences. This analysis, which sampled 2.3% of the total TBG genome, failed to reveal differences in fragment size among the 6 TBG-deficient and 6 normal males examined. One restriction endonuclease (NcoI) identified normal sequences at the putative promoter region of the gene, and four other endonucleases (TaqI, SstII, MspI, and HpaII) recognized the cytosine-guanine dinucleotide phosphate sequences representing potential mutation hot spots. Although C was methylated at these sites, no C to T (thymidine) transitions were found. These data suggest that large deletions, insertions, or rearrangements of the TBG gene, or mutations at sites of methylated cytosine-guanine dinucleotide phosphate dimers are not common mechanisms for inherited complete TBG deficiency in man.
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PMID:Detection of the thyroxine-binding globulin (TBG) gene in six unrelated families with complete TBG deficiency. 290 29

Deficiency of ornithine transcarbamylase (OTC; EC 2.1.3.3), a hepatic mitochondrial enzyme involved in the detoxification of ammonia, is a severe inborn error of metabolism. It is an X-linked disorder which results characteristically in ammonia intoxication, protein intolerance and mental retardation. Early death of affected hemizygous male infants is common, while clinical manifestations in heterozygous females are variable due to random X-chromosome inactivation. Prenatal diagnosis by amniocentesis has not been feasible because OTC is not expressed in amniocytes and because no unusual metabolites can be detected in amniotic fluid. Fetal liver biopsy has been performed for some families at risk, but the dangers inherent in this procedure severely limit its usefulness. In this report, we describe the use of a nearly full-length cloned human cDNA to begin to characterize normal and mutant human OTC genes. One of 15 affected males was found to have a partial deletion of the OTC gene. Two distinct restriction fragment length polymorphisms (RFLPs) were identified at the OTC locus using the restriction endonuclease MspI; 69% of women tested were heterozygous for one or both polymorphisms. Identification of these common polymorphisms makes it possible to offer prenatal diagnosis to a large fraction of obligate carriers and to provide information on carrier status to some females at risk.
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PMID:Gene deletion and restriction fragment length polymorphisms at the human ornithine transcarbamylase locus. 298 25

DNA sequences of the X-chromosome-linked hypoxanthine phosphoribosyltransferase (HPRT) and glucose 6-phosphate dehydrogenase (G6PD) genes have revealed the presence of clusters of CpG dinucleotides, raising the possibility that such clusters are involved in the control of expression of these genes, which are expressed in all tissues. Although CpG clusters are not exclusive features of the X chromosome, the analysis of X-linked genes provides the means to determine whether CpG clusters are control elements; one of the two homologous X loci in female mammals is not expressed, so that active and inactive versions of the gene can be compared. In fact, it has been shown that these CpG clusters are undermethylated when the gene is active and extensively methylated when the gene is inactive. In addition to hypomethylation, chromatin hypersensitivity to endonuclease digestion is a known hallmark of regulatory sequences in eukaryotic genes. We report here that the CpG clusters of the active hprt and g6pd genes are not only undermethylated, but also hypersensitive to MspI, DNase I and S1 nuclease, further supporting the suggestion that they are involved in the control of expression of these genes.
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PMID:Clusters of CpG dinucleotides implicated by nuclease hypersensitivity as control elements of housekeeping genes. 298 78

Compensation is a mechanism by which the X-chromosome nucleolus organizer region of Drosophila melanogaster can increase its ribosomal DNA content up to twofold. It occurs in somatic cells under specific genetic conditions and is mediated by a defined genetic site, the compensatory response locus. The In- and various type I ribosomal DNA repeat units were separated by restriction endonuclease digestion. Comparison of the percentages of these repeat unit types between compensating and noncompensating genotypes showed the same distribution. Therefore no selective amplification of these repeat unit types occurs during ribosomal DNA compensation. These results demonstrate that two processes of rDNA amplification in somatic cells, compensation and independent rDNA polytenization, are exclusive events.
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PMID:Nonselective amplification of ribosomal DNA repeat units in compensating genotypes of Drosophila melanogaster. 643 64

The clonal composition of cancers of the female reproductive tract was evaluated by analysis of patterns of X-chromosome inactivation. Using DNA extracted from frozen tissues or paraffin-embedded archival specimens as template, polymerase chain reaction (PCR) was performed to generate amplified DNA fragments of exon 1 of the X-linked androgen receptor gene, which contains a highly polymorphic trinucleotide repeat. Predigestion of tumor DNA with methylation-sensitive restriction endonuclease Hha I or Hpa II permitted selective PCR amplification from the methylated (uncleaved) allele. Of a total of 54 tumors analyzed, 50 cases showed heterozygosity (93%) and were therefore informative for clonal analysis. Monoclonal composition of the tumors was suggested in a total of 49 of 50 cases, including 12 adenocarcinomas of the uterine endometrium, 13 squamous cell carcinomas of the uterine cervix, 6 adenocarcinomas of the uterine endocervix, and 18 epithelial tumors of the ovary. However, polyclonal composition was observed in one mucinous carcinoma of the ovary, in which we previously showed that both GGT-->GAT and GGT-->GTT mutations are present in > 20% of total K-ras copies in the tissue. Our studies demonstrate the utility of PCR amplification of highly polymorphic repetitive sequences for analysis of patterns of X-chromosome inactivation. This approach is practical for the analysis of clonal cell composition in a high proportion of both formalin-fixed and frozen archival tissues.
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PMID:Analysis of clonality by amplification of short tandem repeats. Carcinomas of the female reproductive tract. 786 41

In order to investigate the clonality in various benign, precancerous and malignant breast lesions, we analyzed small DNA samples from paraffin sections of various breast lesions by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) of the X-chromosome-linked phosphoglycerokinase (PGK) gene. DNA from the lesion as well as from the adjacent normal tissue were analyzed in each case. Two restriction endonucleases. Hpa-II, a methylation sensitive restriction enzyme and Bst XI, a restriction endonuclease, which recognizes this polymorphic site on the PGK gene, were used. Of 19 cases, one case of in situ ductal Ca (DCIS), two cases of invasive ductal Ca and one case of multifocal ductal Ca were shown to be monoclonal. Two cases of intraductal papillomas were found to be polyclonal. One case of atypical ductal hyperplasia showed no conclusive findings. Additionally DNA was not yielded from 3 cases and other 7 cases were not informative, derived from females homozygotes. Further study of a larger number of cases is in progress.
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PMID:Clonal analysis by PCR and RFLP in breast cancer and precancerous lesions. Preliminary data. 904 17

Desmoid tumor is a locally aggressive, nonmetastasizing soft tissue tumor. Whether desmoid tumor is a truly neoplastic cellular proliferative process or, alternatively, an unchecked reactive process has been a subject of debate. In order to determine whether desmoid tumor is composed of a clonal cell population as opposed to being a polyclonal reactive process, analysis of patterns of X-chromosome inactivation was performed. Hematoxylin and eosin stained sections of paraffin-embedded, formalin-fixed tissues were microdissected to obtain both lesional and normal control samples, and the genomic DNAs were extracted by proteinase K digestion. Following treatment with methylation sensitive restriction endonuclease (Hha I or Hpa II), the genomic DNAs were amplified by polymerase chain reaction (PCR), using nested primers targeted to a highly polymorphic short tandem repeat (STR) of the human androgen receptor (HUMARA). In eight of 12 cases, PCR amplification of the genomic DNAs was successful, and all eight of the amplified cases were heterozygous in the size of the HUMARA target. The remaining cases could not be studied because of failure to amplify DNA. Following digestion with HhaI or Hpa II, uniform patterns of X-chromosome inactivation were found in all eight desmoid tumors, whereas normal control tissue remained heterozygous. These results confirm a clonal composition of the tumors. The demonstration of clonality in the tumors in all eight informative cases indicates that desmoid tumor is a true neoplastic process, not an unchecked polyclonal reactive process.
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PMID:Desmoid tumor is a clonal cellular proliferation: PCR amplification of HUMARA for analysis of patterns of X-chromosome inactivation. 906 Jun

The true nature of nevocellular nevus is still unknown and it has been ambiguously classified as a neoplasm or a hamartoma. We studied the clonality of nevocellular nevus and melanoma (malignant melanoma), using an expression-based clonality analysis at the X-linked genes by means of polymerase chain reaction. DNA was extracted from cryostat sections of 20 nevocellular nevi (10 compound and 10 intradermal type) and five melanomas from female patients. A polymorphic portion of the inactivated X-linked gene was amplified after selective digestion of the active X-chromosome with a methylation-sensitive restriction enzyme, Hpa II. Paternal- and maternal-derived fragments were resolved with electrophoresis using the polymorphic restriction endonuclease (BstX I) site for the phosphoglycerate kinase assay, and using the difference of CAG repeats for the human androgen-receptor gene assay. Both assays revealed that all informative nevocellular nevi were polyclonal in origin and all melanomas were monoclonal. Results of the clonality were independent of either the histologic type of nevocellular nevus or whether the nevocellular nevus was of congenital or acquired origin. Thus, nevocellular nevus, congenital or acquired, may be a hamartomatous rather than a neoplastic lesion. The analysis of clonality could be applied to the differential diagnosis of benign melanocytic disease and melanomas.
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PMID:Clonality in nevocellular nevus and melanoma: an expression-based clonality analysis at the X-linked genes by polymerase chain reaction. 934 95

The polymerase chain reaction was used to amplify fragments comprising the known reading frame of the nematode nicotinic acetylcholine alpha-subunit gene tar-1. Sequences were derived from DNA prepared from bulk collections of worms and from individual male and female Trichostrongylus colubriformis. In each case a levamisole-resistant (BCk) and a drug susceptible population were examined. Although several nucleotide transitions were detected no amino acid sequence variations were found between the isolates and between individual worms, indicating that the coding sequence of this gene is not responsible for levamisole-resistance in the isolate tested. However, an intronic allelic T/C variation at position 4955 was observed in both populations. It has been reported that levamisole-resistance in the BCk isolate of T. colubriformis is due to a sex-linked recessive gene or gene complex. A restriction fragment length polymorphism formed by the allelic variation was found and was detectable by digestion with the restriction endonuclease NlaIII. Statistical comparison of allele frequencies from individual male and female worms was consistent with sex-linkage of tar-1 (P < 0.05) but showed no correlation with levamisole resistance status. The polymorphism described will provide a useful X-chromosome marker and represents the first mapped genetic locus in this species.
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PMID:The nicotinic acetylcholine alpha-subunit gene tar-1 is located on the X chromosome but its coding sequence is not involved in levamisole resistance in an isolate of Trichostrongylus colubriformis. 947 89


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