Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In addition to being regulated by a complex array of cis- and trans-acting factors, c-myc protooncogene expression may be modulated by antisense RNA transcripts. Our previous studies have determined that depletion of intracellular polyamines by alpha-difluoromethylornithine results in a marked decrease in the transcription of the human c-myc gene. Because of reports that antisense transcription occurs in the 5' and 3' regions of this gene, we used a genomic clone of the human c-myc gene to ascertain whether polyamine depletion might induce an antisense RNA transcript. These studies demonstrate that polyamine depletion of the human colon cancer cell line COLO 320 results in induction of an endogenous RNA transcript with high homology to the antisense strand of the second intervening sequence (PvuII-RsaI) of the c-myc gene. Furthermore, during such depletion, steady state levels of this transcript vary inversely to the sense direction c-myc RNA. RNase protection studies suggest that the antisense transcript may arise from a different gene locus than the c-myc gene. To further identify the origins of this RNA, a cDNA library was generated from size-selected RNA and screened with c-myc sequences. A 438-base pair cDNA was isolated with approximately 85% homology, to a 285-base region in the second intron of the c-myc gene. Computer homology analysis further reveals that a 120-base region within this cDNA also has approximately 85% homology to the antisense strands of a number of genes, including the growth-related genes, N-myc, p53, and thymidine kinase. These studies provide the initial characterization of an endogenous antisense RNA transcript which could influence cell growth by modulating the expression of c-myc and other genes.
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PMID:Characterization of an endogenous RNA transcript with homology to the antisense strand of the human c-myc gene. 137 45

A polymerase chain reaction (PCR)-mediated RNase protection analysis was performed to detect subtle genetic alterations of p53 in medullary thyroid carcinoma (MTC) and pheochromocytoma. None of the 30 pheochromocytomas showed abnormal RNase protection patterns. Only one of 32 MTCs showed an abnormal pattern, and subsequent DNA sequencing of the PCR product revealed that it had a G to C transversion in codon 49 that resulted in a change from aspartic acid to histidine. However, this was a sporadic MTC with no specific clinicopathological characteristics. On the basis of a previous report that genes on chromosome 17p were not deleted in MTCs and were relatively infrequently deleted in pheochromocytomas, our results suggest that the p53 gene is not involved in tumorigenesis of MTC or pheochromocytoma.
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PMID:Inactivation of the p53 gene is not required for tumorigenesis of medullary thyroid carcinoma or pheochromocytoma. 148 23

Anaplastic carcinoma of the thyroid gland, which is one of the most aggressive, malignant tumors in humans, is considered to originate from preexisting differentiated thyroid cancer. To define the genetic alterations associated with such progression, we examined nine cases of anaplastic thyroid carcinoma for mutation in exons 4-9 of the p53 tumor suppressor gene. Preliminary screening for mutation by RNase protection analysis demonstrated that two out of nine anaplastic carcinomas contained sequence alterations in the p53 gene. Subsequent DNA sequencing identified the mutated nucleotides in these two cases; one was a nonsense mutation at codon 165, and the other was a single-base deletion at codon 176 resulting in the creation of a stop codon downstream due to frameshift. The fact that no mutations were detected in coexisting foci of papillary carcinomas from the same patients shows that these mutations of the p53 gene occurred after development of papillary carcinomas. These results suggest that p53 gene mutation triggers the progression from differentiated into anaplastic carcinoma in the human thyroid gland.
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PMID:p53 gene mutations associated with anaplastic transformation of human thyroid carcinomas. 148 45

The p53 gene was examined in primary or metastatic tumors from six patients with rhabdomyosarcoma (RMS) and in five RMS cell lines by screening methods including single-strand conformation polymorphism analysis, the RNase protection assay, sequencing of complementary DNA subclones, and Southern blotting. Six original tumors were of embryonal histology, four alveolar, and one mixed. p53 mutations were identified in four of the six tumors or cell lines derived from tumors with embryonal histology and in one of the four with alveolar histology. Consistent with p53 allele loss, each mutation was found in the homo- or hemizygous state. One tumor showed a G to C transversion at p53 codon 213 (arginine to proline), and another showed deletion of the entire gene. The p53 mutations in cell lines included a codon 248 C to T transition (arginine to tryptophan) in RD and a codon 280 A to T transversion (arginine to serine) in RH30. The cell line CTR contained a 4-base pair deletion at codons 219/220 in exon 6 with resultant frame shift and premature termination in exon 7. These data support the role of diverse types of p53 mutations in the pathogenesis and/or progression of a significant proportion of cases of childhood RMS.
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PMID:Frequency and diversity of p53 mutations in childhood rhabdomyosarcoma. 155 27

We explored the state of the p53 gene in gastric cancer. Using one or more methods, we examined 15 specimens from primary carcinomas (14 tumors, one cell line), five cell lines derived from metastases, and seven paired samples of nonmalignant gastric mucosa. Sequence analyses of complementary DNA containing the entire p53 gene open reading frame demonstrated abnormalities in one of five samples from primary tumors and in all five samples from metastases. The single cell line derived from a primary carcinoma had no abnormality of the gene. The six abnormalities included four point mutations, one base-pair deletion resulting in a frame shift, and a 24 base-pair deletion caused by an intronic point mutation (as determined by sequence analysis of genomic DNA). Four of the six mutations mapped to regions highly conserved among species or involved in simian virus 40 T-antigen binding. Restriction fragment length polymorphism studies confirmed that chromosome 17p allelic deletions occur only in a minority of primary tumors, but that they may occur more frequently in metastases. Northern blotting and ribonuclease protection assays detected only a fraction of the p53 gene abnormalities detected by sequencing. Our findings indicate that mutations of the p53 gene are relatively rare in primary gastric tumors but appear to be relatively frequent in cell lines derived from metastatic lesions. Our results may help in understanding the molecular events associated with progression and metastasis in gastric carcinoma.
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PMID:Occurrence of p53 gene abnormalities in gastric carcinoma tumors and cell lines. 167 61

Twenty-six primary breast tumors were examined for mutations in the p53 tumor suppressor gene by an RNase protection assay and nucleotide sequence analysis of PCR-amplified p53 complementary DNAs. Each method detected p53 mutations in the same three tumors (12%). One tumor contained two mutations in the same allele. Single strand conformation polymorphism analysis of genomic DNA and complementary DNA proved more sensitive in the detection of mutations. Combining this technique with the other two a total of 12 mutations in the p53 gene were demonstrated in 11 tumors (46%), and a polymorphism at codon 213 was detected in another tumor. Loss of heterozygosity on chromosome 17p was detected by Southern blot analysis in 30% of the tumor DNAs. Not all of the tumors containing a point mutation in p53 also had loss of heterozygosity of the remaining allele, suggesting that loss of heterozygosity may represent a later event.
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PMID:Mutations in the p53 gene in primary human breast cancers. 168 43

We have previously shown that the carboxyl-terminal tryptic peptide of the tumor suppressor p53 coeluted from reverse-phase high-performance liquid chromatography (HPLC) with ribonucleotides, suggesting the possible linkage of RNA to p53. In this report, we establish that p53 is covalently linked to RNA, using biochemical criteria at the levels of both tryptic peptide and intact protein: the electrophoretic properties of a tryptic peptide containing phosphorylated Ser-389 and the HPLC chromatographic properties of p53 depend on the linked RNA, p53, purified through urea-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and HPLC, copurifies with RNA, and Ser-389 liberates ribonucleotides upon RNase or alkali treatment. Wild-type and mutant p53s from both simian virus 40 (SV40)-transformed and SV40-nontransformed cells are RNA linked, indicating that RNA linkage may be a general property of p53. The RNA is labeled in vivo with 3H-uridine and in vitro by RNA ligase, suggesting that the RNA is bound by a 5' linkage. The RNA is a long-lived, integral component of p53 rather than a transient reaction intermediate. RNA linkage occurs at an evolutionarily conserved site on p53. We propose that RNA-linked p53 is a major biologically active form of p53 and that its interaction with RNA-linked SV40 T antigen reflects a role in RNA metabolism.
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PMID:The tumor suppressor p53 is bound to RNA by a stable covalent linkage. 170 9

The p53 gene was examined in primary lymphoblasts of 25 pediatric patients with acute lymphoblastic leukemia by the RNase protection assay and by single strand conformation polymorphism analysis in 23 of 25 cases. p53 mutations were found to occur, but at a low frequency (4 of 25). While all four mutations were identified by single strand conformation polymorphism, the comparative sensitivity of RNase protection was 50% (2 of 4). Heterozygosity was retained at mutated codons in 3 of 4 cases. One pedigree was consistent with the Li-Fraumeni syndrome, and bone marrow from both diagnosis and remission indicated a germline G to T transversion at codon 272 (valine to leucine). Although members of another family were affected with leukemia, a 2-bp deletion in exon 6 was nonhereditary. The other two nonhereditary p53 mutations included a T to G transversion at codon 270 (phenylalanine to cysteine) and a G to C transversion at codon 248 (arginine to proline). These data support the role of both hereditary and acquired p53 mutations in the pathogenesis and/or progression of some cases of childhood acute lymphoblastic leukemia.
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PMID:Hereditary and acquired p53 gene mutations in childhood acute lymphoblastic leukemia. 173 52

The p53 gene initially was thought to be an oncogene, but recent evidence suggests that wild-type p53 can function as a tumor suppressor gene in lung, colon, and breast cancer as well as less common malignancies. This study reports the first identification of intronic point mutations as a mechanism for inactivation of the p53 tumor suppressor gene. Abnormally sized p53 mRNAs found in a small cell and a non-small cell lung cancer cell line were characterized by sequence analysis of cDNA/PCR products, the RNase protection assay and immunoprecipitation. These mRNAs were found to represent aberrant splicing leading to the production of abnormal or no p53 protein. Sequence analysis of genomic DNA revealed that a point mutation at the splice acceptor site in the third intron or the splice donor site in the seventh intron accounts for the abnormal mRNA splicing. In one patient the same intronic point mutation was found in the tumor cell line derived from a bone marrow metastasis and in multiple liver metastases but not in normal DNA, indicating that it occurred as a somatic event before the development of these metastases. These findings further support the role of inactivation of the p53 gene in the pathogenesis of lung cancer and indicate the role of intronic point mutation in this process.
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PMID:Identification of intronic point mutations as an alternative mechanism for p53 inactivation in lung cancer. 216 47

Point mutations in genes can be etiologic of pulmonary diseases, as in the case of the inherited disorders alpha-1-antitrypsin deficiency and cystic fibrosis or in the context of dominant and recessive oncogenes in lung cancer. Various methodologies have been developed to screen for single-base mutations. These techniques include direct DNA sequencing, RNase protection, denaturing gradient gel electrophoresis, and chemical mismatch cleavage. The latter method offers the advantages of rapid and efficient analysis of genomic or cDNA and is thus ideally suited to screening applications. Furthermore, all possible single-base changes can theoretically be detected. In the present work, chemical mismatch cleavage was utilized to detect mutations in the p53 gene in small cell and non-small cell lung cancer. This technique was modified by using a two-step, hemi-nested PCR procedure for preparation of target genomic DNAs permitting an expanded target size for analysis. Evaluation by chemical mismatch cleavage of eight p53 cDNAs derived from lung tumors shown to have different mutations by DNA sequencing correctly detected the presence of a point mutation in all instances. Analysis of six additional tumor genomic DNAs with defined mutations in the corresponding p53 cDNAs accurately confirmed the mutation at the level of the genome. The technique also identified codon 72 and intron 6 polymorphisms. Using the intron 6 polymorphism, loss of heterozygosity at the p53 locus in tumor DNA was readily detected by chemical mismatch cleavage. Finally, utilizing this technique for scanning analysis of the p53 gene of uncharacterized lung tumor DNAs, additional mutations were identified in a prospective manner which were confirmed by sequence analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A chemical mismatch cleavage method useful for the detection of point mutations in the p53 gene in lung cancer. 222 98


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