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At least 811 records · Page 45Linked to original sources
PubMed1993

Inactivation of erythropoietin receptor function by point mutations in a region having homology with other cytokine receptors.

The cytoplasmic domain of the erythropoietin receptor (EpoR) contains a region, proximal to the transmembrane domain, that is essential for function and has homology with other members of the cytokine receptor family. To explore the functional significance of this region and to identify critical residues, we introduced several amino acid substitutions and examined their effects on erythropoietin-induced mitogenesis, tyrosine phosphorylation, and expression of immediate-early (c-fos, c-myc, and egr-1) and early (ornithine decarboxylase and T-cell receptor gamma) genes in interleukin-3-dependent cell lines. Amino acid substitution of W-282, which is strictly conserved at the middle portion of the homology region, completely abolished all the functions of the EpoR. Point mutation at L-306 or E-307, both of which are in a conserved LEVL motif, drastically impaired the function of the receptor in all assays. Other point mutations, introduced into less conserved amino acid residues, did not significantly impair the function of the receptor. These results demonstrate that conserved amino acid residues in this domain of the EpoR are required for mitogenesis, stimulation of tyrosine phosphorylation, and induction of immediate-early and early genes.

Amino Acid Sequence↗
PubMed2003

Glanzmann's thrombasthenia due to a point mutation within intron 10 results in aberrant splicing of the beta3 gene.

Glanzmann's thrombasthenia (GT) is an hereditary bleeding disorder caused by a quantitative or qualitative defect in the integrin alphaIIbbeta3. We attempted to identify genetic defects responsible for a case of GT in Korea. The patient was a 6-year-old boy who had suffered from hemorrhage and purpura. The cDNAs of alphaIIb and beta3 were amplified by reverse transcription (RT)-PCR and were sequenced. RT-PCR of COS7 cells transfected with Exontrap vectors containing the beta3 genomic DNA fragments were performed to verify an aberrant splicing. Transient expression of alphaIIbbeta3 on transfected-COS7 cells was determined by flow cytometry, and the presence of alphaIIbbeta3 was confirmed by immunoprecipitation. We discovered an abnormality with the insertion of 38 bp between exon 10 and exon 11, including a stop codon, in beta3 cDNA. Sequence analysis of genomic DNA showed a point mutation, G-->T, at the position 29 107 of intron 10. RT-PCR analyses of COS7 cells transfected with Exontrap vector containing the mutant beta3 gene revealed that the point mutation at the position 29 107 of intron 10, G-->T, was responsible for an aberrant splicing in the beta3 gene. The transfection experiments and immunoprecipitation revealed the absence of alphaIIbbeta3 in the COS7 cells transfected with mutant gene. The mutation at the position 29 107 of intron 10, G-->T, in the beta3 genomic DNA was found to induce an aberrant splicing and to be responsible for GT in this patient.

Alternative Splicing↗
PubMed1994

Point mutations distal to the processing site affect Drosophila pre-5 S RNA processing. Long range cooperation and a breathing model.

Drosophila pre-5 S RNA, which consists of five conserved stem-loop domains and a 15-nucleotide 3' tail, is 3'-end processed to 120 nucleotide mature 5 S RNA before ribosome assembly. Large deletions in stems II and III, all of stems IV and V, and loop C prohibit Drosophila 5 S RNA processing; deletion of stem IV and half of V does not (Preiser, P. R., and Levinger, L. (1991a) J. Biol. Chem. 266, 7509-7516). Several point mutations in stem I reduce, while certain neighboring sequence changes stimulate, processing (Levinger, L., Vasisht, V., Greene, V., and Arjun, I. (1992) J. Biol. Chem. 267, 23683-23687). Herein we extend this 5 S RNA fine structure analysis to regions farther from the processing site. Most point mutations in loop B, stem III, and loop C severely inhibit processing. One loop C substitution stimulates processing; when combined with stimulatory sequence changes in stem I and loop A, these dispersed mutations improve processing manyfold, perhaps by stabilizing a required conformation or strengthening a protein-binding site. Central stem II sequence changes inhibit processing; several adjacent sequence substitutions which weaken base pairing improve processing. Combining these results with earlier work from stem I and loop A, we hypothesize that slight reduction in base pairing may improve groove access of polypeptide chains to essential contact positions.

Animals↗
PubMed1999

[Detection of three common G6PD gene point mutations in Guangdong province by using ARMS].

OBJECTIVE: To detect three common G6PD gene point mutations, G1388A, G1376T and A95G, in Guangdong province and to estimate the approximate frequencies. METHODS: Using the amplification refractory mutation system(ARMS) method to detect G1388A and G1376T and the newly developed ARMS to identify A95G mutation. RESULTS: Ninety cases of G6PD deficient male were examined, and 42 of them were identified to be G1388A(46.7%), 14 G1376T(15.6%), and 12 A95G(13.3%). Totally 68 out of the 90 cases(75.6%) were of the three common mutations. The rest belong to rare or undefined mutations. CONCLUSION: ARMS method can be used in detecting common mutations of G6PD gene with the benefits of simple, fast, economic, and accurate.

Alleles↗
PubMed1991

Rapid localization of point mutations in PCR products by chemical (HOT) modification.

Our studies of mutational mechanisms in mammalian cells use the AS52 Chinese hamster ovary cell line. AS52 mutants can be selected as 6-thioguanine resistant colonies and mutations are studied at a chromosomally integrated gpt locus. Mutant gpt sequences are amplified using the polymerase chain reaction (PCR) to distinguish deletions from putative point mutations. PCR is efficiently performed from a few thousand lysed cells or from isolated genomic DNA. Amplified mutant PCR fragments carrying putative point mutations are further characterized by localizing the site of the mutation using chemical modification. A heteroduplex molecule consisting of one wild-type and one mutant DNA strand is generated. A base mismatch will be produced at the site of the mutation. Mismatched cytosine or thymine residues are sensitive to modification by hydroxylamine or osmium tetroxide, respectively. The modified DNA heteroduplex is then sensitive to piperidine cleavage. If one strand is 32P-end labeled, then the cleavage product can be separated on a denaturing acrylamide sequencing gel and visualized using autoradiography. Thus, the site of a mutation can be localized to a specific region of the gene, thereby simplifying the DNA sequence analysis and facilitating the rapid generation of mutational sequence spectra.

Animals↗
PubMed1985

Point mutations implicate repeated sequences as essential elements of the CYC7 negative upstream site in Saccharomyces cerevisiae.

The transcription of the CYC7 gene of Saccharomyces cerevisiae, encoding the iso-2-cytochrome c protein, is controlled by two upstream regulatory elements, a positive element and a negative element. The nature of the DNA sequences in the negative element were investigated in a two-part approach. The first involved the construction of a CYC7-galK fusion gene which placed the coding sequence of the Escherichia coli galactokinase gene under the regulation of the CYC7 upstream sequences. This fusion allowed the quantitation by galactokinase enzyme assays of the effects on gene expression of a variety of previously isolated deletion mutations within the negative site. The results suggested that the negative site contained three related sequences. This hypothesis was tested in the second part of these studies, the selection of point mutations within the region of the negative site which led to increased CYC7 expression. Point mutations were introduced by a technique which induced mutations within a localized region at high efficiency. All but one of the mutations involved more than a single base-pair change. The mutations followed the pattern that multiple base-pair changes occurred in one repeat or single base-pair changes occurred in two repeats, with the exception of one mutant, which had a single base-pair change in one repeat. This pattern of mutations and the base pairs that were altered strongly supported the hypothesis that the repeats are integral elements of the negative site.

Base Sequence↗
PubMed2002

Identification of novel point mutations in ERK2 that selectively disrupt binding to MEK1.

Extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2) are essential components of pathways through which signals received at membrane receptors are converted into specific changes in protein function and gene expression. As with other members of the mitogen-activated protein (MAP) kinase family, ERK1 and ERK2 are activated by phosphorylations catalyzed by dual-specificity protein kinases known as MAP/ERK kinases (MEKs). MEKs exhibit stringent specificity for individual MAP kinases. Indeed, MEK1 and MEK2 are the only known activators of ERK1 and ERK2. ERK2 small middle dotMEK1/2 complexes can be detected in vitro and in vivo. The biochemical nature of such complexes and their role in MAP kinase signaling are under investigation. This report describes the use of a yeast two-hybrid screen to identify point mutations in ERK2 that impair its interaction with MEK1/2, yet do not alter its interactions with other proteins. ERK2 residues identified in this screen are on the surface of the C-terminal domain of the kinase, either within or immediately preceding alpha-helix G, or within the MAP kinase insert. Some mutations identified in this manner impaired the two-hybrid interaction of ERK2 with both MEK1 and MEK2, whereas others had a predominant effect on the interaction with either MEK1 or MEK2. Mutant ERK2 proteins displayed reduced activation in HEK293 cells following epidermal growth factor treatment, consistent with their impaired interaction with MEK1/2. However, ERK2 proteins containing MEK-specific mutations retained kinase activity, and were similar to wild type ERK2 in their activation following overexpression of constitutively active MEK1. Unlike wild type ERK2, proteins containing MEK-specific point mutations were constitutively localized in the nucleus, even in the presence of overexpressed MEK1. These data suggest an essential role for the MAP kinase insert and residues within or just preceding alpha-helix G in the interaction of ERK2 with MEK1/2.

Animals↗
PubMed1996

A point mutation in the human transporter associated with antigen processing (TAP2) alters the peptide transport specificity.

The heterodimeric transporter associated with antigen processing (TAP1/TAP2) translocates peptides from the cytosol into the endoplasmic reticulum where loading of major histocompatibility complex class I molecules takes place. TAP transporters from different species are known to exhibit distinct transport specificities with regard to the C-terminal amino acid (aa) of peptides. Thus, human TAP (hTAP), and rat TAP (rTAP) containing the rTAP2a allele are rather promiscuous, whereas mouse TAP (mTAP), and rTAP containing the rTAP2a allele are restrictive and select against peptides with C-terminal small polar/hydrophobic or positively charged aa. The structural basis for this selectivity is not clear. To assess the relative contribution of the TAP1 and TAP2 subunits to transport specificity, we have constructed and analyzed interspecies TAP hybrids and point mutants of hTAP2 expressed in Sf9 insect cells and in TAP-deficient T2 cells. Transport assays with 20 C-terminal variants of the peptide RYWANATRSX showed that: first, transport specificity with regard to C-terminal aa is mainly influenced by TAP2, but TAP1 can also contribute. Second, the selective transport of peptides with C-terminal positively charged aa is critically controlled by the amino-terminal region (1-361) on the TAP2 chain, while transport of peptides with C-terminal small polar/hydrophobic aa is determined by residues located within as well as outside the region 1-361. Third, a single point mutation in hTAP2 (374A-->D) resulted in a drastic alteration of the transport pattern. These results indicate that both TAP1 and TAP2 contribute to efficient peptide transport and that single point mutations in hTAP2 are able to alter the peptide transport specificity. This opens the possibility that naturally occurring mutations in one of the hTAP subunits may alter epitope selection in vivo.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

A point mutation in the RNA-binding domain I results in decrease of PKR activation in acute lymphoblastic leukemia.

RNA-dependent protein kinase (PKR) mediates the antiviral activity of interferon and also has implications in cell growth, differentiation, and apoptosis. On the other hand, the tumor suppressor function of PKR is still controversial. PKR is a serine/threonine kinase that contains two RNA-binding domains (RBD-I and RBD-II) and RBD-I is critical for its activation. Site-directed mutagenesis studies indicated that a single amino acid substitution in RBD-I is sufficient to abolish the interaction of human PKR with RNA. Also, PKR mutants that are unable to bind RNA are inactive in vitro and have no antiproliferative activity in vivo. There have been no reports of mutations in the RNA-binding domains of PKR of tumor cells taken directly from patients. We investigated the presence of mutations in the RBD-I and RBD-II of PKR gene in children with acute lymphoblastic leukemia (ALL). The RNA extracted from bone marrow samples of 15 patients with ALL (5 patients T-lineage; 10 patients B-lineage) was used for to synthesize cDNA and amplify the sequences corresponding to RBD-I and RBD-II. The PCR products were subsequently cloned and sequenced. A point mutation was detected in the RBD-I of PKR from a patient with ALL of T-cell lineage that is located at cDNA nt 50 A --> G (17 Tyr-->Cys). We also found that activation of a PKR mutant by the polyinosinic acid:polycytidylic acid (poly I:C) is impaired when compared with the wild-type PKR. Additional work is required to elucidate whether this point mutation plays a role in the formation and/or maintenance of leukemic cells. To our knowledge, this study is the first example of detection of a mutation in the RBD-I of PKR gene from tumor cells taken directly from patients.

Base Sequence↗
PubMed2001

Point mutation in the stalk of angiotensin-converting enzyme causes a dramatic increase in serum angiotensin-converting enzyme but no cardiovascular disease.

BACKGROUND: Angiotensin-converting enzyme (ACE) metabolizes many small peptides and plays a key role in blood pressure regulation. Elevated serum ACE is claimed to be associated with an increased risk for cardiovascular disease. Previously, two families with dramatically increased serum ACE were described, but no systematic survey of affected individuals was performed, and the molecular background of this trait is unknown. METHODS AND RESULTS: Eight families were identified with autosomal dominant inheritance of a dramatic (5-fold) increase of serum ACE activity. Strikingly, no clinical abnormalities were apparent in the affected subjects. Isolated blood cells were used for genetic and biochemical analysis. The level of ACE expression on the blood leukocytes and dendritic cells and total cell-associated ACE of the affected individuals was similar to that in nonaffected relatives; however membrane-bound mutant ACE was much more efficiently clipped from the cell surface compared with its wild-type counterpart. A point mutation causing Pro1199Leu in the stalk region of the ACE molecule cosegregates with the increase in serum ACE (LOD score, 6.63). CONCLUSIONS: A point mutation in the stalk region of the ACE protein causes increased shedding, leading to increased serum ACE, whereas cell-bound ACE is unaltered, and affected individuals exhibit no clinical abnormalities. These findings qualify the importance of serum ACE and establish a new determinant of ACE solubilization.

Adult↗
PubMed1999

Two novel point mutations of mitochondrial tRNA genes in histologically confirmed Parkinson disease.

Mutations in mitochondrially encoded tRNA genes have been described in a variety of neurological disorders. One such mutation, the A to G transition at nucleotide position 4336 of the mitochondrial tRNA(Gln) gene, has been associated with both Alzheimer and Parkinson disease. We have now performed a complete sequence analysis of all 22 mitochondrially encoded tRNA genes in 20 cases of histologically proven idiopathic Parkinson disease. Genomic DNA extracted from the substantia nigra of frozen or formalin-fixed and paraffin-embedded brains was used for amplification by polymerase chain reaction followed by automated sequencing. Two new homoplasmic point mutations were detected in the genes for tRNA(Thr) (15950 G/A) and tRNA(Pro) (15965 T/C) in 1 patient each. Restriction enzyme digestion revealed absence of the 15950 G/A mutation in 96 controls and in 40 cases of neuropathologically confirmed Alzheimer disease. The 15965 T/C mutation was shown to be absent from 100 control subjects and 47 Alzheimer cases. In addition to the two novel mutations, six known sequence variants were detected in a total of 6 different patients in the genes for tRNA(Asp) (G7521A, 1), tRNA(Arg) (T10463C, 1), tRNA(LeuCUN) (A12308G, 2), and tRNA(Thr) (A15924G, 1; G15928A, 2), including 1 patient carrying the tRNA(Gln) (A4336G) mutation. The G15950A transition affects position 70 of the aminoacyl acceptor stem of tRNA(Thr), which has been implicated as a recognition element for threonyl-tRNA synthetase and, at least in some tRNAs, in the processing of primary mitochondrial transcripts. The T15965C point mutation in the mitochondrial tRNA(Pro) gene alters position 64 of the TpsiC stem. The corresponding nucleotide in bacterial aminoacyl-tRNAs is involved in the interaction with elongation factor Tu. Thus, the two novel mutations are likely to be of functional relevance and could contribute to dopaminergic nerve cell death in affected individuals.

Aged↗
PubMed1999

Differential display, subtractive hybridization, and application of methodology to search for point mutations to identify genetic defects responsible for progression in MCF10AT model of human breast disease.

We describe initial studies utilizing three methods to detect differences in gene expression: (i) differential display with polyT-anchored primers; (ii) differential display with RNA arbitrarily primed polymerase chain reaction (RAP-PCR), and (iii) cDNA subtractive hybridization. Subtractive hybridization, which detects qualitative differences in gene expression, revealed no differences between a human cell line (MCF10A), originated by spontaneous immortalization of breast epithelial cells, and MCF10CA1 cells, a recently derived fully malignant, metastatic variant. The standard method of differential display with polyT anchored primers detected in excess of 100 differentially displayed bands but differential expression could seldom be verified by Northern blotting. However, RAP-PCR products frequently represent the coding region and fewer bands are detected. One gene of interest is a zinc finger protein which may be expressed more in the preneoplastic lesion-forming cells than in nonlesion-forming cells. Because most bands are not consistently differentially displayed among the variants of the MCF10 model, we suspect that point mutations rather than differential quantitative gene expression is responsible for some stage of progression. We propose that differential display of RAP-PCR products on nondenaturing gels might also detect point mutation differences.

Breast Diseases↗
PubMed1991

Haemophilia B Leyden arising de novo by point mutation in the putative factor IX promoter region.

Haemophilia B Leyden is characterized by severe factor IX deficiency during childhood with partial resolution at puberty or following the administration of anabolic steroids. The disorder has recently been associated with point mutations in the putative factor IX promoter region, which contains an imperfect direct repeat spanning a possible start site of transcription. We have identified a T to C transition at position +8 in the promoter region of a patient with the haemophilia B Leyden phenotype. A mutation at this site has not been previously reported and occurs within the repeat consensus sequence in the transcribed but untranslated portion of the gene. There is no family history of haemophilia and sequence analysis of his mother and other family members indicates that the mutation has arisen de novo in this patient. This observation provides further support for a causal relationship between point mutations in the presumptive promoter region of the factor IX gene and the Leyden phenotype.

Adult↗
PubMed1997

Macrolide resistance in Helicobacter pylori: rapid detection of point mutations and assays of macrolide binding to ribosomes.

Resistance of Helicobacter pylori to macrolides is a major cause of failure of eradication therapies. Single base substitutions in the H. pylori 23S rRNA genes have been associated with macrolide resistance in the United States. Our goal was to extend this work to European strains, to determine the consequence of this mutation on erythromycin binding to H. pylori ribosomes, and to find a quick method to detect the mutation. Seven pairs of H. pylori strains were used, the parent strain being naturally susceptible to macrolides and the second strain having acquired an in vivo resistance during a treatment regimen that included clarithromycin. The identity of the strains was confirmed by random amplified polymorphic DNA testing with two different primers, indicating that resistance was the result of the selection of variants of the infecting strain. All resistant strains were found to have point mutations at position 2143 (three cases) or 2144 (four cases) but never on the opposite DNA fragment of domain V of the 23S rRNA gene. The mutation was A-->G in all cases except one (A-->C) at position 2143. Using BsaI and BbsI restriction enzymes on the amplified products, we confirmed the mutations of A-->G at positions 2144 and 2143, respectively. Macrolide binding was tested on purified ribosomes isolated from four pairs of strains with [14C]erythromycin. Erythromycin binding increased in a dose-dependent manner for the susceptible strain but not for the resistant one. In conclusion we suggest that the limited disruption of the peptidyltransferase loop conformation, caused by a point mutation, reduces drug binding and consequently confers resistance to macrolides. Finally, the macrolide resistance could be detected without sequencing by performing restriction fragment length polymorphism with appropriate restriction enzymes.

Anti-Bacterial Agents↗
PubMed1993

True hermaphroditism in a 46,XY individual, caused by a postzygotic somatic point mutation in the male gonadal sex-determining locus (SRY): molecular genetics and histological findings in a sporadic case.

Recently, the gene for the determination of maleness has been identified in the sex-determining region on the short arm of the Y chromosome (SRY) between the Y-chromosomal pseudoautosomal boundary (PABY) and the ZFY gene locus. Experiments with transgenic mice confirmed that SRY is a part of the testis-determining factor (TDF). We describe a sporadic case of a patient with intersexual genitalia and the histological finding of ovotestes in the gonad, which resembles the mixed type of gonadal tissue without primordial follicle structures. The karyotype of the patient was 46,XY. By PCR amplification, we tested for the presence of PABY, SRY, and ZFY by using DNA isolated from peripheral blood leukocytes and for the presence of SRY by using DNA obtained from histological gonadal slices. The SRY products of both DNA preparations were further analyzed by direct sequencing. All three parts of the sex-determining region of the Y chromosome could be amplified from leukocytic DNA. The patient's and the father's SRY sequences were identical with the published sequence. In the SRY PCR product of gonadal DNA, the wild-type and two point mutations were present in the patient's sequence, simulating a heterozygous state of a Y-chromosomal gene: one of the mutations was silent, while the other encoded for a nonconservative amino acid substitution from leucine to histidine. Subcloning procedures showed that the two point mutations always occurred together. The origin of the patient's intersexuality is a postzygotic mutation of the SRY occurring in part of the gonadal tissue. This event caused the loss of the testis-determining function in affected cells.

Adult↗
PubMed2000

A new human malignant peripheral nerve sheath tumour-cell line, HS-sch-2, harbouring p53 point mutation.

Only a few human malignant peripheral nerve sheath tumour (MPNST)-cell lines have been reported, and their characteristics have not been fully established. In this study, we established a new human cell line, HS-Sch-2, from an MPNST of the ordinary type which arose in a 54-year-old woman without von Recklinghausen's disease. This cell line was characterized by chromosome analysis, immunohistochemistry, ultrastructural examination, and direct sequencing of the p53 gene. The HS-Sch-2 cells have grown for more than 48 months in vitro, and exhibited hypotriploid karyotypes with complex chromosome abnormalities lacking a specific pattern. Histological features of the heterotranplanted nude mouse tumours were essentially the same as those of the original MPNST, with positive reactions for S-100 protein and neuron-specific enolase but not for epithelial membrane antigen, fibronectin or CD34. Ultrastructural examination in vivo revealed intricate interdigitation of long cytoplasmic processes and basal lamina-like structures. In addition, direct sequencing of the p53 gene detected a point mutation from CGT to CAT at codon 273 in exon 8. This HS-Sch-2 cell line, which exhibits distinctive morphological characteristics of MPNST and a p53 point mutation, will be useful for biological and pathological investigations of MPNST.

Animals↗
PubMed1996

A hamster temperature-sensitive G1 mutant, tsBN250 has a single point mutation in histidyl-tRNA synthetase that inhibits an accumulation of cyclin D1.

BACKGROUND: We have previously isolated a series of temperature-sensitive mutants for cell-proliferation from the BHK21 cell line, derived from the golden hamster. These mutants proliferate at 33.5 degrees C, the permissive temperature, but not at 39.5 degrees C the restrictive temperature. Using DNA-mediated gene transfer, human genes complementing these ts mutants were cloned. RESULTS: At 39.5 degrees C the tsBN250 cell line, a temperature-sensitive mutant of the BHK21 cell line, had a defect in the G1 phase, but not in the S phase. The human gene complementing tsBN250 cells was found to encode histidyl-tRNA synthetase. Indeed, the tsBN250 cell line had a single base change--guanine to adenine at the second position of the 362nd codon of hamster histidyl-tRNA-synthetase, converting arginine to histidine. Following release from serum starvation, cyclin E, but not cyclin D1, was accumulated, while, at 39.5 degrees C, the mRNA of cyclin D1 was normally expressed in tsBN250 cells. A similar inhibition of cyclin D1 accumulation was observed in another ts mutant, tsBN269, which has a single point mutation in lysyl-tRNA synthetase. Overexpression of cyclin D1 enabled tsBN250 cells to enter the S phase. CONCLUSION: tsBN250 cells have a single point mutation in histidyl tRNA synthetase that causes a loss of histidyl-tRNA synthetase activity which in turn reduces the content of cyclin D1, but not of cyclin E, thereby resulting in G1 arrest.

Amino Acid Sequence↗
PubMed1997

[No point mutation of the 2.8 kb EcORI fragment of the nasopharyngeal carcinoma transforming gene TX in nasopharyngeal carcinoma].

We have previously cloned a nasopharyngeal carcinoma transforming gene from human nasopharyngeal carcinoma cell line CNE-2 using mouse JB6 cell line as the recipient cells. This transforming gene, designated Tx, exhibits moderate transforming activity upon transfection into JB6 cells. Several lines of evidence indicate that the 2.8 kb EcoRI fragment which lies in the middle of the Tx gene is responsible for the transforming activity. The sequence of the 2.8 kb EcoRI fragment was determined, which showed striking homology with the human immunoglobulin light chain C region gene. Using the modified polymerase chain reaction-single strand conformation polymorphism analysis (PCR-SSCP) silver staining technique, we studied the possible point mutations of the nasopharyngeal carcinoma gene Tx in nasopharyngeal carcinoma. No mobility shift was detected in eleven paired cases of nasopharyngeal carcinoma biopsies suggesting that in most cases of nasopharyngeal carcinoma, the Tx gene is not activated via a mode of point mutation. Taken together with the previously obtained results we have found that the Tx gene is not activated by gene rearrangement or gene amplification. Therefore, we consider that the Tx gene may have been activated by its interaction with other regulatory factors.

Carcinoma, Squamous Cell↗