Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Allelic deletions in the nm23, a metastasis suppressor gene, are known to occur in neuroblastomas, breast and colorectal carcinomas. Down-regulation of nm23 expression has been reported in various rodent and human tumor cells with high metastasis phenotype. Colorectal tumors showed overexpression of nm23. To elucidate the regulatory mechanisms of nm23, we isolated, cloned and sequenced the presumptive regulatory DNA fragment spanning the 5' region of the human nm23-H1 gene. The region's nucleotide sequence shows the presence of motifs typical for transcriptional elements such as TFIID, AP-1 and CTF/NF1. A common transcription initiation site is located at -136 upstream from the first ATG codon in placenta tissue, in breast, colorectal, prostate tumor cell lines and in primary colorectal tumor. Multiple transcription start sites were identified in tumor cell lines and colorectal tumor. When the promoter element was linked to a reporter gene, chloramphenicol acetyltransferase (CAT) and transfected in human 2fTGH cells, strong CAT activity was detected, which also showed that the presence of AP-1 and CTF/NF1 elements are essential for promoter activity. A detailed study of the structure and function of the promoter element of the nm23-H1 gene will help in understanding the regulatory mechanisms of nm23 expression and its role in tumor progression, especially in metastasis.
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PMID:Isolation and characterization of the promoter region of human nm23-H1, a metastasis suppressor gene. 808 95

We isolated genomic clones of two isotypes of human NDP kinase, nm23-H1 and H2. The nm23-H1 and H2 genes located in a tandem array contained 5 exons and most of the splicing sites in the exon-intron junctions of two isotypes were essentially identical. The regulatory elements of nm23-H1 and H2 genes were also analysed. One major and several minor transcriptional initiation sites were detected in the two isotypes by 5' RACE analysis in HeLa cell. We also identified them by means of an RNase protection assay and primer extension analysis. Promoter activities were found in the 5' flanking sequences of the two genes when placed upstream of the chloramphenicol acetyltransferase gene. Transcriptional activities of nm23-H1 and H2 regulatory regions were measured in a series of human cancer lines. The nm23-H1/nm23-H2 gene transcriptional activity ratio varied depending on the cell line. DNA sequencing of these two genes showed that their promoter regions contain distinct binding sites for known transcriptional factors. These studies suggest that the two isotypes of the nm23 genes might be regulated dissimilarly, and in cell type specific manner.
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PMID:Independent and differential expression of two isotypes of human Nm23: analysis of the promoter regions of the nm23-H1 and H2 genes. 893 40

DR-nm23 cDNA was cloned recently by differential screening of a cDNA library derived from chronic myelogenous leukemia-blast crisis primary cells. It is highly homologous to the putative metastasis suppressor nm23-H1 gene and the closely related nm23-H2 gene. When overexpressed in the myeloid precursor 32Dcl3 cell line, it inhibited granulocyte colony-stimulating factor-stimulated granulocytic differentiation and induced apoptosis. We have now found that the expression of DR-nm23 is not restricted to hematopoietic cells but is also detected in an array of solid tumor cell lines, including carcinoma of the breast, colon, and prostate, as well as the glioblastoma cell line T98G. We have also isolated both the gene and its 5'-flanking region and found that DR-nm23 localizes on chromosome 16q13. The gene consists of six exons and five introns. When fused in-frame to the nucleotide sequence for the green fluorescent protein and transfected in SAOS-2 cells, it generates a protein of the predicted size that localizes to the cytoplasm. The 5'-flanking region of DR-nm23 does not contain a canonical TATA box or a CAAT box, but it is G+C rich and contains two binding sites for the developmentally regulated transcription factor activator protein 2 (AP-2). Transient expression assays of DR-nm23 promoter-chloramphenicol acetyltransferase constructs demonstrated that the segment from nucleotides -1028 to +123 has the highest activity in hematopoietic K562 cells and in TK-ts13 hamster fibroblasts. Moreover, AP-2 induced a 3-fold transactivation of the DR-nm23 5'-flanking segment from nucleotides -1676 to +123 and interacted specifically with oligomers containing putative AP-2 binding sites (-936 to -909, and -548 to -519) as indicated by electrophoretic mobility shift assay. Furthermore, nuclear run-on assays from high and low DR-nm23-expressing cells (K562 and CCRF-CEM, respectively) revealed similar transcription rates. Therefore, the regulation of the DR-nm23 gene expression might involve other mechanisms occurring at posttranscriptional and/or translational levels.
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PMID:Gene structure, promoter activity, and chromosomal location of the DR-nm23 gene, a related member of the nm23 gene family. 906 90