Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In trypanosomatids, DNA replication in the nucleus and in the single mitochondrion (or kinetoplast) initiates nearly simultaneously, suggesting that the DNA synthesis (S) phases of the nucleus and the mitochondrion are coordinately regulated. To investigate the basis for the temporal link between nuclear and mitochondrial DNA synthesis phases the expression of the genes encoding DNA ligase I, the 51 and 28 kDa subunits of replication protein A, dihydrofolate reductase and the mitochondrial type II topoisomerase were analyzed during the cell cycle progression of synchronous cultures of Crithidia fasciculata. These DNA replication genes were all expressed periodically, with peak mRNA levels occurring just prior to or at the peak of DNA synthesis in the synchronized cultures. A plasmid clone (pdN-1) in which TOP2, the gene encoding the mitochondrial topoisomerase, was disrupted by the insertion of a NEO drug-resistance cassette was found to express both a truncated TOP2 mRNA and a truncated topoisomerase polypeptide. The truncated mRNA was also expressed periodically coordinate with the expression of the endogenous TOP2 mRNA indicating that cis elements necessary for periodic expression are contained within cloned sequences. The expression of both TOP2 and nuclear DNA replication genes at the G1/S boundary suggests that regulated expression of these genes may play a role in coordinating nuclear and mitochondrial S phases in trypanosomatids.
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PMID:Periodic expression of nuclear and mitochondrial DNA replication genes during the trypanosomatid cell cycle. 770 2

Gene expression in trypanosomatids appears to be regulated largely at the posttranscriptional level and involves maturation of mRNA precursors by trans splicing of a 39-nucleotide miniexon sequence to the 5' end of the mRNA and cleavage and polyadenylation at the 3' end of the mRNA. To initiate the identification of sequences involved in the periodic expression of DNA replication genes in trypanosomatids, we have mapped splice acceptor sites in the 5' flanking region of the TOP2 gene, which encodes the kinetoplast DNA topoisomerase, and have carried out deletion analysis of this region on a plasmid-encoded TOP2 gene. Block deletions within the 5' untranslated region (UTR) identified two regions (-608 to -388 and -387 to -186) responsible for periodic accumulation of the mRNA. Deletion of one or the other of these sequences had no effect on periodic expression of the mRNA, while deletion of both regions resulted in constitutive expression of the mRNA throughout the cell cycle. Subcloning of these sequences into the 5' UTR of a construct lacking both regions of the TOP2 5' UTR has shown that an octamer consensus sequence present in the 5' UTR of the TOP2, RPA1, and DHFR-TS mRNAs is required for normal cycling of the TOP2 mRNA. Mutation of the consensus octamer sequence in the TOP2 5' UTR in a plasmid construct containing only a single consensus octamer and that shows normal cycling of the plasmid-encoded TOP2 mRNA resulted in substantial reduction of the cycling of the mRNA level. These results imply a negative regulation of TOP2 mRNA during the cell cycle by a mechanism involving redundant elements containing one or more copies of a conserved octamer sequence within the 5' UTR of TOP2 mRNA.
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PMID:Sequences within the 5' untranslated region regulate the levels of a kinetoplast DNA topoisomerase mRNA during the cell cycle. 894 27

mRNA levels of several Crithidia fasciculata genes involved in DNA metabolism have previously been found to cycle as cells progress through the cell cycle. Octamer consensus sequences in the 5' untranslated regions (5' UTRs) of these transcripts were shown to be required for cycling of these mRNAs. The KAP3 gene encodes a kinetoplast histone H1-like DNA binding protein, and its mRNA levels cycle in parallel with those of the kinetoplast DNA topoisomerase (TOP2), dihydrofolate reductase-thymidylate synthase (DHFR-TS), and the large subunit of the nuclear single-stranded DNA binding protein (RPA1). KAP3 mRNA contains two octamer consensus sequences in its 3' UTR but none in its 5' UTR. Mutation of these octamer sequences was not sufficient to prevent cycling of a sequence-tagged KAP3 mRNA expressed from a plasmid. Mutation of an octamer sequence contained on the precursor transcript but not on the mRNA, in addition to mutation of the two octamer sequences in the 3' UTR, was necessary to abolish cycling of the mRNA. The requirement for a sequence not present on the mature mRNA indicates that regulation of the mRNA levels by the octamer sequences occurs at or prior to splicing of the transcript. Incompletely processed RNAs containing octamer sequences were also found to accumulate during the cell cycle when the mRNA levels were lowest. These RNA species hybridize to both the KAP3 coding sequence and that of the downstream drug resistance gene, indicating a lack of processing within the intergenic region separating these genes. We propose a cell cycle-dependent interference in transcript processing mediated by octamer consensus sequences as a mechanism contributing to the cycling of such transcripts.
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PMID:Sequence elements in both the intergenic space and the 3' untranslated region of the Crithidia fasciculata KAP3 gene are required for cell cycle regulation of KAP3 mRNA. 1291 86

Patients with non-muscle invasive bladder cancer (NMIBC) generally have a high risk of relapsing locally after primary tumor resection. The search for new predictive markers of local recurrence thus represents an important goal for the management of this disease. We studied the copy number variations (CNVs) of 24 oncogenes (MDM4, MYCN, ALK, PDGFRA, KIT, KDR, DHFR, EGFR, MET, SMO, FGFR1, MYC, ABL1, RET, CCND1, CCND2, CDK4, MDM2, AURKB, ERBB2, TOP2A, AURKA, AR and BRAF) using multiplex ligation probe amplification technique to verify their role as predictive markers of recurrence. Formalin-fixed paraffin-embedded tissue samples from 43 patients who underwent transurethral resection of the bladder (TURB) were used; 23 patients had relapsed and 20 were disease-free after 5 years. Amplification frequencies were analyzed for all genes and MDM4 was the only gene that showed significantly higher amplification in non recurrent patients than in recurrent ones (0.65 vs. 0.3; Fisher's test p=0.023). Recurrence-free survival analysis confirmed the predictive role of MDM4 (log-rank test p=0.041). Our preliminary results indicate a putative role for the MDM4 gene in predicting local recurrence of bladder cancer. Confirmation of this hypothesis is needed in a larger cohort of NMIBC patients.
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PMID:Copy number analysis of 24 oncogenes: MDM4 identified as a putative marker for low recurrence risk in non muscle invasive bladder cancer. 2502 75

Research on the amplification of oncogenes in thymic malignant tumor is limited. In this study, we aimed to determine the gene amplification status of receptor tyrosine kinases and other cell regulator genes in thymic malignant tumors, with a view toward the future introduction of molecular targeted therapy. In addition, we examined the usefulness of multiplex, ligation-dependent probe amplification (MLPA) in the semi-comprehensive detection of these gene amplifications. The participants of this study were nine patients with thymic carcinoma and one patient with atypical carcinoid who underwent resection at our department from 1999 to 2016. Twenty-four oncogenes (MDM4, MYCN, ALK, PDGFRA, KIT, KDR, DHFR, EGFR, MET, SMO, BRAF, FGFR1, MYC, ABL1, RET, CCND1, CCND2, CDK4, MDM2, AURKB, ERBB2, TOP2A, AURKA, AR) were analyzed for amplification by MLPA. In cases where amplification by MLPA was suspected, confirmation was performed by fluorescence in situ hybridization (FISH). Immunostaining for detected oncoproteins and p53 were performed in cases with confirmed oncogene amplification. MYC (2/10, 20%) and MDM2 (1/10, 10%) amplifications were detected using MLPA and FISH. Immunostaining in both cases was positive. The MDM2-amplified tumor relapsed and spread rapidly after operation despite the use of post-operative chemo-radiotherapy. MYC amplification may be involved in the carcinogenesis of thymic malignant tumors. In addition, MDM2 amplification may be a concern in the increased malignancy.
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PMID:Semi-comprehensive analysis of gene amplification in thymic malignant tumors using multiplex ligation-dependent probe amplification and fluorescence in situ hybridization. 3250 76