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

The cis-acting regulatory elements of the osteonectin gene have been studied using a chloramphenicol acetyltransferase (CAT) promoter assay in osteonectin-expressing and nonexpressing cultured cells. When various stretches of the promoter were transiently transfected into fetal bovine bone cells, a positive element was detected in the DNA located between bases -504 and 11 (1 being the start of transcription) and a negative element between bases -900 and -504. The positive element of the promoter also conferred preferential expression of the gene, showing more activity in cells with higher levels of osteonectin mRNA expression. A 1.2 kb fragment of intron 1 displayed a negative effect on CAT expression when inserted 5' to the promoter. An additional regulatory element was found in DNA encoding exon 1, which significantly influenced expression of the gene in fetal bovine bone cells. Gel shift analysis using positive genomic elements located 5' to the start of transcription indicated that one of the nuclear proteins that interacts with the osteonectin promoter may be related to the transcription factor AP2.
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PMID:Expression of the osteonectin gene potentially controlled by multiple cis- and trans-acting factors in cultured bone cells. 179 60

A nontransformed rat clonal cell line (UMR-201) with phenotypic characteristics of osteoblastic precursor cells was found to respond to insulinlike growth factor 1 (IGF-1) by increased osteonectin and pro-alpha 1(I)-collagen mRNA expression. Cells were treated for 24 h with insulin, growth hormone, or IGF-1 to study the regulation of messenger RNA for osteonectin and pro-alpha 1(I)-collagen using Northern blot hybridization. UMR-201 cells possess specific high-affinity receptors for growth hormone, although there were no significant effects of growth hormone (10(-9)-10(-7) M) or insulin (10(-9)-10(-6) M) on mRNA species for osteonectin or pro-alpha 1(I)-collagen. However, IGF-1 increased both mRNA species from a concentration of 10(-9) M. The effect on osteonectin mRNA expression was likely due to increased transcription; when 5' flanking osteonectin (ON) genomic fragments were linked to the bacterial reporter gene chloramphenicol acetyltransferase (CAT) and introduced by transfection into UMR-201 cells, the transcriptional activity of the ON-CAT construct was increased 235 and 270% by 10(-8) and 10(-7) M IGF-1, respectively. In contrast, growth hormone did not change the transcriptional activity of the ON-CAT construct. In confirmation of other work, transforming growth factor beta (TGF-beta, 0.1-2.5 ng/ml) increased mRNA for osteonectin and pro-alpha 1(I)-collagen in a dose-dependent manner. Transforming growth factor alpha (TGF-alpha) at 0.1-10 ng/ml had no consistent effects in repeated experiments on osteonectin and pro-alpha 1(I)-collagen mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Insulinlike growth factor 1 regulates mRNA levels of osteonectin and pro-alpha 1(I)-collagen in clonal preosteoblastic calvarial cells. 220 53

To understand the basis of osteonectin (SPARC) transcriptional regulation, we have isolated a bovine genomic clone (lambda Og15) encoding exon 1 and 15 kilobase pairs (kb) of flanking DNA. Direct RNA sequencing of the 5' end of the osteonectin message showed it contained a sequence identical to that of a 2.4-kb EcoRI-BamHI fragment located midway in the clone lambda Og15. The results indicate exon 1 is located 10 kb away from exon 2 in the bovine genome. The DNA sequence unit CCTG is repeated five times in exon 1 which is composed exclusively of untranslated sequence. Sequence analysis of the 5'-flanking DNA revealed the presence of many regulatory motifs including a "GC" box with four overlapping SP1 consensus sequences. Immediately downstream from the GC box is a 72-base pair purine-rich stretch composed primarily of direct repeats of the sequence motifs GGGGA and GGA (GAGA box). Digestion of the flanking DNA in vitro with S1 endonuclease showed a site for the enzyme at position -55 which is just 3' to the GAGA box. Chimeric chloramphenicol acetyltransferase constructs were prepared containing the S1-sensitive site and showed substantial transcriptional activity in UMR-106 and fetal and adult human bone cells which are known to be high producers of the protein. The results indicate a potential regulatory activity of the S1 site in osteonectin gene activation.
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PMID:Osteonectin promoter. DNA sequence analysis and S1 endonuclease site potentially associated with transcriptional control in bone cells. 253 44

UMR 201 is a nontransformed rat clonal cell line derived from neonatal calvaria with phenotypic characteristics of preosteoblasts. Retinoic acid strongly induces expression of alkaline phosphatase and its mRNA in these cells. Dexamethasone substantially reduced the retinoic acid-induced expression of alkaline phosphatase. This apparent interaction between dexamethasone and retinoic acid effects raised the possibility that interactions may extend to other osteoblast-related phenotypic characteristics in UMR 201 cells. Treatment with dexamethasone resulted in a decrease in the expression of mRNA for pro-alpha 1(I) collagen, but upon coincubation with 1 microM retinoic acid for 24 h, the decrease in mRNA for pro-alpha 1(I) collagen was abrogated. Dexamethasone (Dex) treatment caused a dose-dependent increase in osteonectin mRNA, half maximally effective between 1 nM and 10 nM Dex. One micromolar of retinoic acid alone led to a small increase in expression of osteonectin mRNA but prevented any further increase when Dex was added to retinoic acid-treated cells. To study transcriptional control, osteonectin genomic fragments were linked to the bacterial reporter gene, chloramphenicol acetyltransferase, and introduced by transfection into UMR 201 cells. Dexamethasone increased the transcriptional activity of an osteonectin-chloramphenicol acetyltransferase construct; 100 nM Dex resulted in a 3-fold increase over control cells which was attenuated when 1 microM retinoic acid was added to the incubation, while retinoic acid alone resulted in a 2-fold increase in transcriptional activity. Finally, it was noted that coincubation with retinoic acid and Dex stimulated the proliferation of UMR 201 cells when compared with either treatment alone. This study shows the potential importance of hormonal interactions in the expression of osteoblast function.
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PMID:Opposing influences of glucocorticoid and retinoic acid on transcriptional control in preosteoblasts. 262 42

We have investigated the role of 5'-flanking DNA sequences in regulating the expression of the murine Sparc (osteonectin) gene in parietal endoderm cells and in F9 embryonal carcinoma cells induced to differentiate into parietal endoderm with retinoic acid and cyclic AMP. Varying lengths of flanking sequences extending up to 3.0 kilobase pairs 5' of the transcription initiation site were linked to the bacterial chloramphenicol transacetylase gene in the Bluescript M13- vector. The constructs were tested in transient assays, using a beta-galactosidase plasmid as a transfection control. Sequences between 78 and 169 base pairs upstream of the cap site are the minimum required for cell-type specific promoter activity; this region is dominated by two oligopurine/oligopyrimidine stretches or "GAGA" boxes and is highly conserved between the mouse and bovine genes. Addition of the sequence between -169 and -449, which includes part or all of a third GAGA box, results in increased parietal endoderm specific transcription, up to a maximum of 6.3-fold higher than in undifferentiated F9 cells. Further addition of sequences between -449 and -638 markedly reduces promoter activity in both cell types but parietal endoderm-specific activity is restored in constructs containing 2.2 and 3.0 kilobase pairs of flanking DNA. In addition, we have identified sequences related to the consensus sequence for steroid response elements, one of which is able to confer progesterone-enhanced transcription when tested with a heterologous promoter in steroid responsive cells. These results suggest that negative and positive elements normally interact to regulate the temporal and tissue-specific patterns of Sparc gene transcription seen in vivo.
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PMID:Evidence for positive and negative regulatory elements in the 5'-flanking sequence of the mouse sparc (osteonectin) gene. 274 36

Two overlapping cosmids have been isolated containing the entire murine gene for SPARC (osteonectin), a Ca2+-binding, phosphorylated glycoprotein associated with extracellular matrix synthesis and remodeling. The gene contains 10 exons and covers 26.5 kilobase pairs of DNA. Exon analysis shows that the two N-terminal glutamic acid-rich sequences which are predicted to undergo conformational change upon binding of calcium, as well as the C-terminal EF-hand Ca2+-binding domain are each encoded by a single exon. Comparative analysis of the exon sequence does not support the idea that the SPARC gene has evolved by shuffling of exons from other Ca2+-binding proteins. The 5' flanking region of the SPARC gene, which promotes transcription when placed in front of the bacterial chloramphenicol acetyltransferase gene, contains neither "TATA" nor "CAAT" box sequences. However, unlike most other genes lacking these motifs, mapping of the 5' end of the SPARC gene by RNase protection and primer extension analysis reveals only a single major and one minor transcription start site. The upstream region to -120 includes six repeats of the sequence GGAGG, two repeats of the sequence 5' GGAGG A/C GGAGGG 3', and a potential transcription factor AP-2 binding site.
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PMID:Characterization of the mouse SPARC/osteonectin gene. Intron/exon organization and an unusual promoter region. 316 75