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)

We previously used mice bearing a myosin light chain-chloramphenicol acetyltransferase (MLC1-CAT) transgene to show that adult muscle cells bear a heritable, cell autonomous memory of their rostrocaudal position. CAT mRNA and protein are expressed in a > 100-fold rostrocaudal gradient in skeletal muscles of developing and adult MLC1-CAT mice (Donoghue, M. J., Merlie, J. P., Rosenthal, N. and Sanes, J. R. (1991). Proc. Natl. Acad. Sci. USA 88, 5847-5851; Donoghue, M. J., Alvarez, J. D., Merlie, J. P. and Sanes, J. R. (1991). J. Cell Biol. 115, 423-434). Moreover, both in primary cultures and in myogenic cell lines prepared from individual muscles of these mice, CAT levels reflect the body position from which the myoblasts were derived (Donoghue, M.J., Morris-Valero, R., Johnson, Y.R., Merlie, J.P. and Sanes, J. R. (1992). Cell 69, 67-77). Here, we show that the methylation state of the MLC1-CAT transgene in skeletal muscles is also graded along the rostrocaudal axis: methylation levels decrease and expression levels increase in the order, jaw-->neck-->chest and forelimb-->hindlimb. Methylation levels are also approx. 10-fold higher in rostrally derived than in caudally derived myogenic cell lines, which express low and high levels of CAT, respectively. Within each cell line, undifferentiated cells (myoblasts), which do not express the transgene, and differentiated cells (myotubes), which do, are indistinguishable in methylation state. Thus, differentiation-related changes in transgene expression do not affect position-related levels of transgene methylation. On the other hand, treatment of rostrally derived lines with the demethylating agent, 5-azacytidine, decreases methylation and increases expression of the transgene. Thus, perturbation of methylation affects expression. Taken together, these results suggest that methylation provides a genomic imprint of rostrocaudal body position that may serve as a component of the positional memory that mammalian cells retain into adulthood.
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PMID:An axial gradient of transgene methylation in murine skeletal muscle: genomic imprint of rostrocaudal position. 129 32

The myosin light chain (MLC) 1/3 enhancer (MLC enhancer), identified at the 3' end of the skeletal MLC1/3 locus, contains a sequence motif that is homologous to a protein-binding site of the skeletal muscle alpha-actin promoter. Gel shift, competition, and footprint assays demonstrated that a CArG motif in the MLC enhancer binds the proteins MAPF1 and MAPF2, previously identified as factors interacting with the muscle regulatory element of the skeletal alpha-actin promoter. Transient transfection assays with constructs containing the chloramphenicol acetyltransferase reporter gene demonstrated that a 115-bp subfragment of the MLC enhancer is able to exert promoter activity when provided with a silent nonmuscle TATA box. A point mutation at the MAPF1/2-binding site interferes with factor binding and abolishes the promoter activity of the 115-bp fragment. The observation that an oligonucleotide encompassing the MAPF1/2 site of the MLC enhancer alone cannot serve as a promoter element suggests that additional factor-binding sites are necessary for this function. The finding that MAPF1 and MAPF2 recognize similar sequence motifs in two muscle genes, simultaneously activated during muscle differentiation, implies that these factors may have a role in coordinating the activation of contractile protein gene expression during myogenesis.
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PMID:The myosin light chain enhancer and the skeletal actin promoter share a binding site for factors involved in muscle-specific gene expression. 204 75

The human gene encoding the alkali myosin light chains (MLC) 1 and 3 of fast skeletal muscle has been isolated. Two separate start sites for transcription have been identified by S1 analysis of muscle RNA. The nucleotide sequences of both proximal promoter regions have been determined and compared to the corresponding gene regions of other species. Several conserved promoter elements were located within 140 nucleotides upstream of the mRNA cap site, whereas further upstream no homologous sequences were found. Unidirectional 5' deletion mutants of both MLC promoters were used to direct bacterial chloramphenicol acetyltransferase activity in transient transfection assays of muscle and nonmuscle cells. Approximately 120 nucleotides of the MLC1 promoter and 80 nucleotides of the MLC3 promoter were sufficient for the transcriptional activation in primary myotubes and to a lower degree also in fibroblasts and hepatocytes. The preferential expression in muscle cells was not dependent on the conserved MLC consensus sequence, CCTTTTATAG, but it absolutely required the CCAT box or the CAT-like box in the MLC1 and MLC3 promoters, respectively. The weak activity of the MLC1 promoter was markedly enhanced in myotubes when DNA from the 3' gene flanking sequence was included in the chloramphenicol acetyltransferase constructs.
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PMID:Identification of the functional promoter regions in the human gene encoding the myosin alkali light chains MLC1 and MLC3 of fast skeletal muscle. 277 79

The rat myosin light chain (MLC)1/3 gene locus contains a potent muscle-specific enhancer, located downstream of the coding region, greater than 24 kilobases away from the MLC1 transcription start site. To assess the role of this enhancer in the activation of MLC expression during development, transgenic mice were generated carrying multiple copies of a MLC1 promoter-chloramphenicol acetyltransferase (CAT) transcription unit linked to a genomic fragment including the enhancer. CAT expression was detected in four mouse lines, up to 1000-fold higher in skeletal muscles than in other tissues. Activation of endogenous MLC1 transcription in these animals 4 days before birth was reflected in the onset of CAT transgene expression. This study identifies the transcriptional control elements necessary to activate the 21-kilobase MLC1/3 locus at the appropriate fetal stage and indicates that the MLC enhancer is sufficient to induce developmentally regulated expression from the MLC1 promoter exclusively in skeletal muscle cells.
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PMID:Myosin light chain enhancer activates muscle-specific, developmentally regulated gene expression in transgenic mice. 281 57

In transgenic mouse embryos, expression of a muscle-specific reporter, consisting of a chloramphenicol acetyltransferase gene linked to regulatory sequences from the rat myosin light chain 1/3 locus (MLC-CAT), is graded in developing axial muscles along the rostrocaudal axis and in cell cultures derived from these muscles. Here we demonstrate that maintenance of positional differences in MLC-CAT transgene expression cannot be attributed to differences in the transcriptional competence of corresponding muscles. Rather, patterns of transgene expression are reflected in the extent of CpG demethylation of both MLC1 promoter and MLC enhancer sequences. Variations in reporter gene expression can be reconstituted by in vitro methylation of specific CpGs in transfected MLC-CAT DNA. As the MLC-CAT transgene is activated during embryogenesis, demethylation of the MLC1 promoter lags behind that of the downstream MLC enhancer, which appears to be the initial target for epigenetic modification. In developing somites, demethylation of the transgenic MLC enhancer is not graded and therefore does not reflect early regional differences in MLC-CAT transgene expression patterns. These studies implicate selective methylation in the maintenance rather than in the establishment of transcriptional differences in developing muscles.
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PMID:Role of methylation in maintenance of positionally restricted transgene expression in developing muscle. 763 67