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Exon

About: Exon is a research topic. Over the lifetime, 38308 publications have been published within this topic receiving 1745408 citations. The topic is also known as: exons.


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Journal ArticleDOI
TL;DR: Results suggest that genetic recombination in the 5' region of the B2m gene is a recurrent mechanism in B1m gene defects, and FO-1 cells represent a useful model for analyzing the role of HLA class I antigens in the biology of melanoma cells and in their interaction with cells of the immune system.
Abstract: The melanoma cell line FO-1 does not express HLA class I antigens and does not acquire them on the cell surface after incubation with IFN-gamma. Immunochemical studies showed that FO-1 cells synthesize HLA class I heavy chain, but do not synthesize beta 2-microglobulin (beta 2-mu). The latter abnormality is associated with lack of beta 2-mu mRNA which remains undetectable in FO-1 cells incubated with IFN-gamma. The defect was identified as a genetic lesion in the B2m gene, since DNA hybridization analysis detected a deletion of the first exon of the 5'-flanking region, and of a segment of the first intron of the B2m gene. HLA class I antigen expression was reconstituted on melanoma cells FO-1 after transfection with the wild-type mouse B2m gene, thereby confirming the abnormality of the endogenous B2m gene. The defect identified in FO-1 cells is distinct from that underlying the lack of HLA class I antigen expression by lymphoblastoid cells Daudi, but is remarkably similar to that causing lack of H-2 class I antigen expression by mouse lymphoblastoid cells R1 (TL-). These results suggest that genetic recombination in the 5' region of the B2m gene is a recurrent mechanism in B2m gene defects. In addition to contributing to our understanding of molecular abnormalities in HLA class I antigen expression by melanoma cells, FO-1 cells represent a useful model for analyzing the role of HLA class I antigens in the biology of melanoma cells and in their interaction with cells of the immune system.

301 citations

Journal Article
TL;DR: The presence of a T allele in exon 7 (position 18067) of the XRCC3 gene was significantly associated with melanoma development, and may provide further insights into the pathogenesis and the mechanism of UV-radiation induced carcinogenesis as well as having a role in prevention.
Abstract: Exposure to UV radiation is a major risk factor for the development of malignant melanoma. DNA damage caused by UV radiation is thought to play a major role in carcinogenesis induction. Multiprotein pathways involved in repairing UV-DNA damage are the base excision, the nucleotide excision, and the homologous double-stranded DNA repair pathways. This study used a sequence-specific primer PCR (PCR-SSP) genotyping method to investigate the association between polymorphisms in DNA repair genes from these pathways with the development of malignant melanoma. The patient cohort was comprised of 125 individuals with malignant melanoma with lesions or staging suggesting a high risk of relapse or metastatic disease. The control population consisted of 211 individuals. We found the presence of a T allele in exon 7 (position 18067) of the XRCC3 gene was significantly associated with melanoma development (P = 0.004; odds ratio, 2.36; relative risk, 1.74). This gene codes for a protein involved in the homologous pathway of double-stranded DNA repair, thought to repair chromosomal fragmentation, translocations, and deletions. These results may provide further insights into the pathogenesis and the mechanism of UV-radiation induced carcinogenesis as well as having a role in prevention.

301 citations

Journal ArticleDOI
TL;DR: Neuropeptide Y mRNA was found in all rat brain subregions tested, which shows that neuropeptid Y is synthesized throughout the brain, and the sequence of the 30-amino acid carboxyl-terminal peptide of preproneuropeptic Y is highly conserved, which suggests that it is functionally important.
Abstract: Neuropeptide Y is a 36-amino acid peptide that is abundant throughout the mammalian nervous system. It belongs to the same family of carboxyl-terminally amidated peptides as pancreatic polypeptide and peptide YY. We describe here the gene encoding the rat neuropeptide Y precursor. The gene spans 7.2 kilobase pairs and contains four exons. The exon organization is identical to the pancreatic polypeptide gene, although the amino acid sequences of the neuropeptide Y and pancreatic polypeptide precursors differ extensively. The predicted amino acid sequence of mature rat neuropeptide Y is identical to the human sequence. Also the sequence of the 30-amino acid carboxyl-terminal peptide of preproneuropeptide Y is highly conserved, which suggests that it is functionally important. Two neuropeptide Y alleles were found to differ at nine positions in 2.5 kilobase pairs at the 5' portion of the gene. No exon difference was found. One nucleotide substitution close to the gene promoter may influence the regulation of expression. Neuropeptide Y mRNA was found in all rat brain subregions tested, which shows that neuropeptide Y is synthesized throughout the brain. Developmentally, mRNA was detected in the rat brain as early as embryonic day 16 and increased rapidly to adult levels. The level of neuropeptide Y mRNA was also studied in several rat peripheral organs. Unexpectedly high levels were observed in heart and spleen. This mRNA may be synthesized in intrinsic ganglia and non-neuronal cells, respectively.

301 citations

Journal ArticleDOI
TL;DR: Interestingly, different exon 20 mutations and coexisting mutations seemed to have a different influence on gefitinib response, but variability exists between different individuals.
Abstract: Purpose: Clinical reports about responsiveness to gefitinib treatment in patients of non-small cell lung cancer (NSCLC) with mutations in exon 20 of epidermal growth factor receptor (EGFR) are limited. To increase understanding of the influence of exon 20 mutations on NSCLC treatment with gefitinib, we investigated the clinical features of lung cancer in patients with exon 20 mutations and analyzed the gefitinib treatment response. Experimental Design: We surveyed the clinical data and mutational studies of NSCLC patients with EGFR exon 20 mutations in the National Taiwan University Hospital and reviewed the literature reports about EGFR exon 20 mutations and the gefitinib treatment response. Results: Twenty-three patients with mutations in exon 20 were identified. Nine (39%) had coexisting mutations in EGFR exons other than exon 20. Sixteen patients received gefitinib treatment, and a response was noted in 4 patients. The gefitinib response rate of NSCLC with exon 20 mutations was 25%, far lower than those with deletions in exon 19 and L858R mutations. Interestingly, different exon 20 mutations and coexisting mutations seemed to have a different influence on gefitinib response. Conclusions: EGFR exon 20 mutations of NSCLC patients result in poorer responsiveness to gefitinib treatment, but variability exists between different individuals.

300 citations

Journal ArticleDOI
22 Sep 1995-Science
TL;DR: It is demonstrated that amino acid sequences contained within the NR1 molecule serve to localize this receptor subunit to discrete membrane domains in a manner that is regulated by alternative splicing and protein phosphorylation.
Abstract: NMDA (N-methyl-D-aspartate) receptors are selectively localized at the postsynaptic membrane of excitatory synapses in the mammalian brain. The molecular mechanisms underlying this localization were investigated by expressing the NR1 subunit of the NMDA receptor in fibroblasts. NR1 splice variants containing the first COOH-terminal exon cassette (NR1A and NR1D) were located in discrete, receptor-rich domains associated with the plasma membrane. NR1 splice variants lacking this exon cassette (NR1C and NR1E) were distributed throughout the cell, with large amounts of NR1 protein present in the cell interior. Insertion of this exon cassette into the COOH-terminus of the GluR1 AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate) receptor was sufficient to cause GluR1 to be localized to discrete, receptor-rich domains. Furthermore, protein kinase C phosphorylation of specific serines within this exon disrupted the receptor-rich domains. These results demonstrate that amino acid sequences contained within the NR1 molecule serve to localize this receptor subunit to discrete membrane domains in a manner that is regulated by alternative splicing and protein phosphorylation.

300 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,618
20222,004
2021905
2020908
2019887
2018909