Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

In vivo regulation of cell cycle dependent human histone gene expression was examined in transgenic mice using a fusion construct containing 6.5 kB of a human H4 promoter linked to the chloramphenicol acetyltransferase (CAT) reporter gene. Transcriptional control of histone gene expression, as a function of proliferative activity, was determined. We established the relationship between DNA replication dependent H4 mRNA levels (Northern blot analysis) and H4 promoter activity (CAT assay) during postnatal development in a broad spectrum of tissues. In most tissues sampled in adult animals, the cellular representation of H4 gene transcripts declined in parallel with promoter activity. This result is consistent with transcriptional control of H4 gene expression at the cessation of proliferation. Interestingly, while H4 mRNA was detectable at very low levels post-proliferatively in brain, promoter activity persisted in adult brain, where most of the cells are terminally differentiated. This dissociation between histone gene promoter activity and histone mRNA accumulation points to the possibility of post-transcriptional regulation of histone gene expression in brain. Cultures of osteoblasts were prepared from calvaria of transgenic mice carrying the H4 promoter/CAT reporter construct. In contrast to the brain, in these bone-derived cells, we established by immunohistochemistry that the transition to the quiescent, differentiated state is associated with a transcriptionally mediated downregulation of histone gene expression at the single cell level.
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PMID:Downregulation of histone H4 gene transcription during postnatal development in transgenic mice and at the onset of differentiation in transgenically derived calvarial osteoblast cultures. 140 Jun 21

Gene H1t encodes a testis-specific variant of the H1 histone family expressed in pachytene spermatocytes during the meiotic phase of spermatogenesis. Fusions between various upstream fragments of the H1t gene and the chloramphenicol acetyltransferase-encoding reporter gene were analyzed in mouse L cells by both transient and permanent transfection. Expression of the minimal promoter [174 nucleotides (nt) upstream from the transcription start point] was enhanced by sequences extending to nt -693, but was reduced in constructs with kb of upstream sequence. Using synchronized cells, expression was at least twofold higher in growing than in inhibited cells. Thus, the H1t promoter is modulated both positively and negatively by distant upstream sequences, and it displays some of the S-phase-dependent character of a replication-dependent histone.
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PMID:Analysis of the promoter for the gene encoding the testis-specific histone H1t in a somatic cell line: evidence for cell-cycle regulation and modulation by distant upstream sequences. 153 53

The gene encoding the human basal histone variant H2A.Z has been cloned and sequenced. There is a single functional H2A.Z gene with several pseudogene copies. No other histone genes were found in the 3 kilobases of upstream sequence or in the 0.7 kilobase of downstream sequence. In the upstream region, there are regions of Alu sequences, located about 1375 and 2650 base pairs before the transcription start site. The amount of the H2A.Z transcript is unlinked to DNA replication; however, the amount of the H2A.Z transcript is greatly decreased as proliferating cell cultures become quiescent due in part to a decrease in the rate of transcription. Promoter sequences upstream from the H2A.Z gene have been delineated in IMR-90 cells by chloramphenicol acetyltransferase gene expression. Maximal promoter activity was found in a chloramphenicol acetyltransferase construct that contained 234 base pairs just upstream from the transcription start site. This region includes two GC boxes and three CCAAT boxes as well as a properly positioned TATA box. The organization of the human gene is similar to that of the recently characterized chicken gene (Dalton, S., Robins, A. J., Harvey, R. P., and Wells, J. R. E. (1989) Nucleic Acids Res. 17, 1745-1756). Both have four introns with identical exon-intron borders, but three of the introns in the chicken gene are much longer than those in the human. The promoter regions of the two genes have little overall homology; however, two GC boxes and one of the CCAAT boxes are conserved.
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PMID:The human histone H2A.Z gene. Sequence and regulation. 169 87

The histone H4t gene is actively transcribed in rat testis germinal cells and in several non-testis cell types including cells from liver. This histone H4 gene is expressed most actively in testis premeiotic pachytene spermatocytes, and its expression is down-regulated in postmeiotic early spermatids. The histone H4 gene promoter is functional as demonstrated by finding significant levels of chloramphenicol acetyltransferase (CAT) mRNA in mammalian cells transiently transfected with a histone H4-promoted CAT expression vector compared to cells transfected with an expression vector lacking of the promoter. Examination of the proximal promoter of the histone H4 gene by electrophoretic mobility shift assays indicates that specific protein-DNA interactions occur when pachytene spermatocyte nuclear proteins are mixed with promoter fragments containing regions designated site I and site II, consensus sequence elements essential for regulating transcription of the histone H4 gene. These specific protein-DNA interactions are eliminated by competition with identical DNA fragments, but are not eliminated by competition with nonhomologous DNA fragments. Significant differences are found in mobility shift patterns upon comparison of nuclear proteins from germinal cell populations enriched in pachytene spermatocytes where the gene is actively expressed and early spermatids where the gene is not expressed.
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PMID:Protein-DNA interactions within the rat histone H4t promoter. 170 21

A 6.86 kb rat genomic DNA fragment containing the testis-specific histone H1t gene and the histone H4t gene has been sequenced. S1-nuclease protection analyses of total cellular RNA from rat liver and testis showed that histone H1t mRNA was present only in testis. Examination of various highly enriched populations of rat testis cell types revealed that H1t mRNA was found exclusively in a fraction enriched in pachytene spermatocytes. When protein, DNA interactions within the proximal promoter region of the histone H1t gene were examined by electrophoretic mobility shift assays, only minor differences were found in mobility shift patterns of the H1t promoter in assays comparing binding of nuclear proteins from pachytene spermatocytes and early spermatids. However, major differences in binding were observed upon comparing nuclear proteins from rat pachytene spermatocytes to liver. Comparison of binding patterns of rat testis, rat hepatoma H4 cells, HeLa cells, and COS-1 cells also revealed dramatic differences. Transcriptional activity of the histone H1t promoter was examined by measuring H1t promoted chloramphenicol acetyltransferase (CAT) mRNA levels in transient expression assays in transfected rat hepatoma H4 cells, HeLa cells, and COS-1 cells. These assays revealed that the histone H1t promoted CAT gene functioned poorly in HeLa cells and COS-1 cells compared to expression with the parent SV40 promoted vector pSV2CAT. The H1t promoted CAT gene apparently did not work at all in transfected rat hepatoma H4 cells, which is consistent with testis germinal cell specific expression of the histone H1t gene.
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PMID:Structural and functional analysis of the rat testis-specific histone H1t gene. 213 96

To determine the involvement of 3'-end structure of mRNA in the regulation of gene expression in eukaryotic cell, a series of pSCAT plasmids was constructed with chloramphenicol acetyltransferase (CAT) gene and the 3'-regulatory elements from various eukaryotic genes. As a result of determination of the CAT activities and the mRNA level generated from these plasmids, both results were well correlated. Furthermore, the treatment of transfected cells with phorbol ester (TPA) revealed that the polyadenylated CAT mRNAs form some genes were stabilized, in contrast, the mRNAs bearing 3'-end structure of histone or C-myc genes were not.
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PMID:Stability of CAT gene transcript depends on the 3'-end structure. 257 46

alpha-skeletal actin message levels have been shown to be tightly regulated in chicken primary myoblast cultures. To test for gene elements required for muscle cell specific expression, DNA sequences containing the 5'-flanking regions of the chicken alpha-skeletal actin, beta-cytoplasmic actin, and the histone H2b genes were linked to the coding sequences of the chloramphenicol acetyltransferase gene and transfected into myogenic and non-myogenic cells. In contrast to beta-actin CAT hybrids, the alpha-skeletal actin CAT constructions displayed restricted CAT expression in transfected non-myogenic cells. We showed that a 411 nucleotide fragment flanking the 5' end of of the alpha-skeletal actin gene was responsible for a 9-15 fold increase in CAT enzymatic activity during myoblast fusion, versus only a transient 2 fold rise for the beta-actin and histone flanking sequences. These results indicate that DNA sequences within 411 bp of the 5' terminus of the alpha-skeletal actin gene influenced its cell type and stage specific expression.
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PMID:Tissue restricted and stage specific transcription is maintained within 411 nucleotides flanking the 5' end of the chicken alpha-skeletal actin gene. 300 79

We examined the structural and functional properties of a human H3 histone gene promoter. The complete nucleotide sequence of an H3 structural gene and 515 nucleotides of 5' and 100 nucleotides of 3' flanking sequences were determined. The upstream region of this cell cycle dependent H3 histone gene, designated pST519, contains consensus sequences typical of genes transcribed by RNA polymerase II. To address promoter function directly, we determined the capability of the 5' flanking sequences to direct the transcription of two genes which are not functionally or structurally related. Fusion genes were constructed using the 5' flanking sequences of this human H3 histone gene and either human beta-globin or bacterial chloramphenicol acetyltransferase (CAT) coding sequences. Both of these fusion genes were expressed when transfected into HeLa cells. Under control of the pST519 histone gene promoter, a beta-globin mRNA transcript was initiated at the appropriate H3 (bp) enhancer, inserted upstream from the histone promoter in both fusion constructs, increased levels of beta-globin and CAT expression. Expression of the pST519 H3 histone gene in COS cells in the absence of the SV40 72-bp enhancer confirmed that the sequences required for promoting transcription reside within the 750-bp 5' flanking sequences and that the exogenous enhancer facilitates, but is not a prerequisite for, transcription. Enhancer-facilitated expression of a cell cycle dependent human H4 histone gene was also observed following transfection into mouse L cells and indicates that the regulatory sequences of human histone genes and transcription factors of mouse cells are compatible.
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PMID:Enhancer-facilitated expression of prokaryotic and eukaryotic genes using human histone gene 5' regulatory sequences. 301 46

We have molecularly cloned the genomic gene encoding the mouse histone variant H2A.X and characterized the promoter. The promoter region of the H2A.X gene was characterized by chloramphenicol acetyltransferase analysis using Balb/c 3T3 cells. Maximal promoter activity was found in the construct containing up to -282 base pairs H2A.X upstream region. Within this region, we found two sequences regulating the promoter activation; one was an E2F site and another was a CCAAT box. These sequences were also required for the DNA/protein binding activities. Thus, these activities corresponded to the promoter activities, implying that the promoter activity H2A.X gene was controlled by both the transcription factor E2F and H1TF2 through the E2F and CCAAT element. The CCAAT box binding activity was constitutive when cell cycle was progressed by release from G1 arrest, but transiently transfected chloramphenicol acetyltransferase activity slightly increased when cells entered S phase. Similarly, the level of the smallest form of E2F (free E2F) became higher when cells reentered the cell cycle, indicating that the free E2F was one capable of inducing the promoter activation. Thus, the free E2F and CCAAT DNA binding activity correlated with regulation of the promoter activity.
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PMID:Regulation of the mouse histone H2A.X gene promoter by the transcription factor E2F and CCAAT binding protein. 764 25

We have investigated the promoter element(s) required by the cell cycle regulated FO108 human histone H4 gene for control of gene expression during adipocyte proliferation and differentiation. Stable 3T3L1 cell lines were established that express fusion genes in which the histone H4 promoter is joined to chloramphenicol acetyltransferase (cat) as a reporter gene. Expression of the H4CAT fusion genes was monitored in proliferating and confluent 3T3L1 preadipocytes and in differentiating 3T3L1 adipocytes. The results indicate that the H4 cell cycle element (CCE), which mediates S phase-specific stimulation of H4 gene transcription, is not required for transcriptional regulation during differentiation. Instead, a minimal H4 promoter (nucleotides -46 to -11) is sufficient to mediate the complex transcriptional response of H4 gene expression observed during the process of adipocyte differentiation of 3T3L1 cells. In addition, the data suggest that down-regulation of histone gene expression during cellular differentiation may be mediated by passive inactivation of the promoter due to loss of positive regulatory factor(s).
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PMID:Histone H4 proximal promoter mediates a complex transcriptional response during differentiation of 3T3L1 adipocytes. 770 76


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