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

---

Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gene encoding PTH-related peptide (PTHrP) is expressed in a wide variety of normal and neoplastic tissues. Increased PTHrP gene expression in and secretion of PTHrP by specific tumors directly contributes to the development of malignancy-associated hypercalcemia in vivo. To define the genetic elements important for the control of PTHrP gene transcription, we used the reverse transcription polymerase chain reaction to delineate the control of promoter utilization and the splicing patterns of the exons encoding 5'-untranslated sequences. The majority of normal and neoplastic human tissues contained PTHrP mRNA transcripts initiating from both the up-stream (P1) and down-stream (P2) human PTHrP promoters. Furthermore, the downstream promoter was preferentially used by a factor of more than 30-fold. P1-initiated transcripts contained RNA species both with and without exon 2 (E2) sequences, except in the pancreas, adrenal, and stomach, where E2-containing sequences predominated. The transcriptional activities of P1, P2, and P1 + P2 were assessed by transfection of the corresponding PTHrP-chloramphenicol acetyltransferase (CAT) fusion genes into heterologous cell lines. Fusion genes containing P2 sequences were more transcriptionally active than fusion genes containing P1 sequences. The transcriptional activities of P1 + P2 in their natural tandem orientation were additive in rat keratinocytes and human JEG choriocarcinoma cells. In contrast, the activity of P1 + P2 was less than that of P2 alone in hamster BHK fibroblasts and InR1-G9 cells, and human HeLa cells. Analysis of the transcriptional properties of 5'-deleted human PTHrP-CAT constructs revealed the presence of multiple positive and negative DNA sequences (within both P1 and P2) functionally important for human PTHrP gene transcription. Distinct positive and negative DNA elements were also identified from analysis of 5'-deleted rat PTHrP-CAT fusion genes. The results of these experiments provide evidence for cell- and tissue-specific utilization of 1) distinct human PTHrP transcription start sites and specific patterns of 5'-exon splicing and 2) multiple positive and negative DNA control elements, important for the regulation of human and rat PTHrP gene transcription.
...
PMID:Regulation of parathyroid hormone-related peptide (PTHrP) gene transcription: cell- and tissue-specific promoter utilization mediated by multiple positive and negative cis-acting DNA elements. 128 Mar 27

The proportion of hexokinase (HK; EC 2.7.1.1) isozyme 1 (HK1) that is bound to the outer mitochondrial membrane is tissue specific and developmentally regulated. HK activity is known to be markedly elevated in many cancer cells and a significant fraction is mitochondrial bound. This study examined the role of the 15-amino acid N-terminal domain of HK1 in binding to liver and hepatoma mitochondria. A chimeric reporter construct, pCMVHKCAT, encoding this HK1 domain coupled to the chloramphenicol acetyltransferase (CAT) gene was electroporated into mouse Hepa 1-6 hepatoma cells. After digitonin treatment, cell fractions were assayed for HK, lactate dehydrogenase, and CAT activities. Digitonin (75 micrograms/mg of protein) caused cytosolic leak but 70% of HK remained with the pellet. HKCAT, like HK, remained predominantly with the pellet; CAT form the control, pCMVCAT, remained mostly unbound. Binding of membrane-free cell extracts to rat liver mitochondria in vitro showed 91% of the HKCAT bound, whereas only 12% of CAT bound. Specificity of HKCAT binding to mitochondria was demonstrated by competition of HK1 for HKCAT binding sites on rat liver mitochondria as well as by blockage of HKCAT binding by N,N'-dicyclohexylcarbodiimide, which covalently binds to porin and blocks HK1 binding. Deletional mutant constructs of HKCAT showed reduced binding with increasing deletion size. In summary, these studies demonstrate that the 15-amino acid N-terminal domain of HK1 is necessary and sufficient to confer mitochondrial binding properties to CAT and that there is specificity for this binding to the mitochondria.
...
PMID:Targeting of hexokinase 1 to liver and hepatoma mitochondria. 130 5

Mutation of the p53 tumor suppressor gene is a recurring event in a variety of human cancers. Wild-type p53 may regulate cell proliferation and has recently been shown to repress transcription from several cellular promoters. We studied the effects of wild-type and mutant human p53 on the human proliferating-cell nuclear antigen promoter and on several viral promoters including the simian virus 40 early promoter-enhancer, the herpes simplex virus type 1 thymidine kinase and UL9 promoters, the human cytomegalovirus major immediate-early promoter-enhancer, and the long terminal repeat promoters of Rous sarcoma virus, human immunodeficiency virus type 1, and human T-cell lymphotropic virus type I. HeLa cells were cotransfected with a wild-type or mutant p53 expression vector and plasmids containing a chloramphenicol acetyltransferase reporter gene under viral (or cellular) promoter control. Expression of wild-type p53 correlated with a consistent and significant (6- to 76-fold) reduction of reporter enzyme activity. A mutation at amino acid 143 of p53 releases this inhibition significantly with all the promoters studied. Expression of a p53 mutated at any one of the five amino acid positions 143, 175, 248, 273, and 281 also correlated with a much smaller (one- to sixfold) reduction of reporter enzyme activity from the herpes simplex virus type 1 thymidine kinase promoter. These mutant forms of p53 are found in various cancer cells. Thus, failure of tumor suppression correlates with loss of the promoter inhibitory effect of p53.
...
PMID:Inhibition of viral and cellular promoters by human wild-type p53. 135 31

A plasmid carrying the 5'-flanking region (-1584 to +47 with respect to the transcription initiation site) of the mouse proliferating cell nuclear antigen (PCNA) gene was fused with the chloramphenicol acetyltransferase (CAT) gene, and then cotransfected into mouse N18TG2 cells with expression plasmids for the adenovirus type 12 E1 genes. Expression of E1A gene products elevated the CAT expression by 5- to 9-fold, but expression of the E1B gene product did not. RNase protection analysis revealed that the activation of the PCNA gene promoter by E1A was at the transcription step. Both the 13S E1A and the 12S E1A activated the PCNA gene promoter, indicating that the activation domain of E1A resides in a common region(s) of 13S and 12S E1A products. The major target region of E1A was mapped within the 68 base-pair region (-21 to +47) of the PCNA gene, which includes consensus sequences for transcription factors PEA3 and E2F, although the upstream region (-83 to -21) including ATF(CREB)-binding consensus had an additional effect in the transactivation.
Jpn J Cancer Res 1992 Jun
PMID:Activation of the mouse proliferating cell nuclear antigen gene promoter by adenovirus type 12 E1A proteins. 135 54

Wild-type p53 has recently been shown to repress transcription from several cellular and viral promoters. Since p53 mutations are the most frequently reported genetic defects in human cancers, it becomes important to study the effects of mutations of p53 on promoter functions. We, therefore, have studied the effects of wild-type and mutant human p53 on the human proliferating-cell nuclear antigen (PCNA) promoter and on several viral promoters, including the herpes simplex virus type 1 UL9 promoter, the human cytomegalovirus major immediate-early promoter-enhancer, and the long terminal repeat promoters of Rous sarcoma virus and human T-cell lymphotropic virus type I. HeLa cells were cotransfected with a wild-type or mutant p53 expression vector and a plasmid containing a chloramphenicol acetyltransferase reporter gene under viral (or cellular) promoter control. As expected, expression of the wild-type p53 inhibited promoter function. Expression of a p53 with a mutation at any one of the four amino acid positions 175, 248, 273, or 281, however, correlated with a significant increase of the PCNA promoter activity (2- to 11-fold). The viral promoters were also activated, although to a somewhat lesser extent. We also showed that activation by a mutant p53 requires a minimal promoter containing a lone TATA box. A more significant increase (25-fold) in activation occurs when the promoter contains a binding site for the activating transcription factor or cyclic AMP response element-binding protein. Using Saos-2 cells that do not express p53, we showed that activation by a mutant p53 was a direct enhancement. The mutant forms of p53 used in this study are found in various cancer cells. The activation of PCNA by mutant p53s may indicate a way to increase cell proliferation by the mutant p53s. Thus, our data indicate a possible functional role for the mutants of p53 found in cancer cells in activating several important loci, including PCNA.
...
PMID:Modulation of cellular and viral promoters by mutant human p53 proteins found in tumor cells. 135 62

The multidrug resistance (MDR1) gene encodes a P-glycoprotein, which catalyzes the energy-dependent efflux of anticancer agents. Various environmental stresses including heat shock can induce the expression of endogenous MDR1 genes. In order to study the regulatory mechanisms of MDR1 gene expression, we have established human cancer KB cell lines which could stably integrate bacterial chloramphenicol acetyltransferase (CAT) gene driven by various lengths of the MDR1 promoter. Kst-6 has an integrated plasmid, pMDRCAT1, containing the human MDR1 promoter of -2 kilobases. The MDR1 gene promoter contains a typical heat shock element (HSE) motif located -152 bp to -178 bp from the initiation site. Heat shock at 45 degrees C for 90 min significantly induced CAT activity in Kst-6 cells. Northern blot analysis showed a 4-5 fold increase in CAT mRNA levels in Kst-6 cells. Deletion analysis of the MDR1 promoter demonstrated that the induction of CAT activity was observed in Kxh-14 cells containing a HSE-deleted MDR1 promoter construct, pMDRCAT7. However, further deletion analysis showed that heat shock could not induce CAT activity in Khp-1 cells containing -76 approximately +121 base sequence of the promoter, suggesting that a new heat shock responsible element was located at between -136 and -76. Gel shift assay showed that the heat shock factor (HSF) could bind to the HSE motif located at -152 bp to -178 bp in the MDR1 promoter. We also found that one distinct DNA-protein complex formed specifically within the MDR1 promoter region -99 to -66 was not significantly increased, but relatively more stabilized under mild denaturing condition in the nuclear extract of heat-shocked cells. In our present assay system, activation of the MDR1 promoter in response to heat shock appears to be mediated through both a new heat shock responsive element and MDR1 specific transcription factor.
...
PMID:Activation of human multidrug resistance-1 gene promoter in response to heat shock stress. 135 36

Both neu gene overexpression and loss of estrogen receptor (ER) expression have been found to correlate with a poor prognosis in human breast cancer. Studies of breast tumor specimens have suggested that these two factors are not independent, leading us to hypothesize that there is a causal relationship between loss of ER and overexpression of neu. In this report, we confirm that ER can negatively regulate the expression of the neu gene protein product, p185neu, in two ER positive but not an ER negative breast cancer cell line(s). We have produced sublines which stably express human ER from a previously ER negative human breast cancer cell line. We demonstrate that the expression of ER in these cell lines is sufficient to confer the ability to respond to estradiol by down-regulating neu expression at both the protein and RNA levels. Utilizing neu promoter-chloramphenicol acetyltransferase constructs in transient cotransfection assays, we have also shown that this regulation occurs at the transcriptional level and requires the presence of both ER and estradiol. Furthermore, utilizing promoter deletion constructs, we provide evidence that a 140-base pair region of the neu promoter is required for this transcriptional regulation. When placed in a heterologous promoter, this 140-base pair region allows transcriptional repression by estradiol stimulated ER; thus, it represents an estrogen responsive region within the neu promoter. Finally, we have used gel mobility shift analysis to demonstrate an alteration in the nuclear factor(s) binding to this promoter region in estradiol stimulated versus estradiol deprived breast cancer cells. This study provides the first evidence that the inverse clinical correlation between neu and ER expression may be due to transcriptional repression of neu by estradiol stimulated ER.
Cancer Res 1992 Dec 01
PMID:Transcriptional repression of the neu protooncogene by estrogen stimulated estrogen receptor. 135 36

The activity of the human O6-methylguanine-DNA methyltransferase (MGMT) gene promoter was determined in eight human cell lines by measuring chloramphenicol acetyltransferase activity in a reporter gene system. MGMT promoter activities in cells that do not express MGMT (Mer-) fell within the range of activities seen in cells that do express MGMT (Mer+). The promoter region contains 11 potential binding sites for the transcription factor Sp1, but no correlation was seen between cellular Sp1 protein and MGMT promoter chloramphenicol acetyltransferase activity. Because Mer- cells are not deficient in the factors needed for transcription of MGMT, we suggest that at least two mechanisms regulate MGMT expression. One suppresses MGMT mRNA and protein in Mer- cells, and another regulates the levels of constitutive expression in Mer+ cells. Sp1 is not a limiting factor in MGMT expression.
Cancer Res 1992 Nov 15
PMID:A comparison of human O6-methylguanine-DNA methyltransferase promoter activity in Mer+ and Mer- cells. 142 89

Most oral contraceptives (OC) contain a progestin in combination with an estrogen, and the progestin component in OC includes one of the following 19-nortestosterone derivatives: norethynodrel; norethindrone; or norgestrel (levonorgestrel). It is well known that estrogens promote the growth of breast cancer. However, progestins have recently also been implicated in the development of breast cancer. We have compared and contrasted the ability of synthetic progestins to stimulate the proliferation of cultured human breast cancer cells and examined their possible mechanism of action. We found that some progestins used in OC were able to stimulate the growth of estrogen receptor-positive (ER+) MCF-7 and T47DA18 human breast cancer cells but not ER- MDA-MB-231, BT-20, and T47DC4 human breast cancer cells. However, two other progestins, MPA and R5020, which are not used in OC, were either not able to stimulate or only slightly stimulated growth. The potency of norethynodrel [median effective dose (EC50) = 4 x 10(-8) M] and norethindrone (EC50 = 3 x 10(-8) M) was greater than norgestrel (EC50 = 2 x 10(-7) M) in MCF-7 cells. E2 (EC50 = 8 x 10(-13) M) was an even more potent stimulator of growth. More importantly, the progestin-induced growth stimulation was blocked by the antiestrogens 4-hydroxytamoxifen and ICI 164,384 but not the antiprogestin 17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)-17 alpha-(1-propynyl)-estra-4, 9-dien-3-one (RU486). To determine whether the proliferative action of progestins was mediated through the ER, cells were transfected with a chloramphenicol acetyltransferase reporter gene containing an estrogen response element derived from vitellogenin 2A gene. The progestins which stimulated the growth of breast cancer cells also increased chloramphenicol acetyltransferase activity. The induction of chloramphenicol acetyltransferase activity was blocked by the addition of the antiestrogens 4-hydroxytamoxifen and ICI 164,384 but not the antiprogestin RU486. This study provides direct evidence that the 19-nortestosterone derivatives in OC have estrogenic properties and suggests that activation of ER, but not progesterone receptor, is the growth-stimulatory mechanism for these synthetic progestins. Our results may help to explain the conflicting evidence linking OC and breast cancer risk. A rigorous evaluation of the "total" estrogenic potential of OC might produce a better correlation with breast cancer risk.
Cancer Res 1992 Dec 01
PMID:Estrogenic potential of progestins in oral contraceptives to stimulate human breast cancer cell proliferation. 142

Although the androgen receptor (AR) has been detected by ligand-binding assays, there is little known about the expression and regulation of the AR gene in human breast-cancer cells. AR mRNA, measured by Northern analysis in 18 cell lines, was found to be expressed predominantly in oestrogen- and progesterone-receptor-positive (ER+, PR+) lines as a single species of approximately 10.5 kb but was also comparatively abundant in I ER- and PR-negative cell line, MDA-MB-453. Dexamethasone (Dex), Organon 2058 (Org 2058), dihydrotestosterone (DHT), and all-trans-retinoic acid (RA) down-regulated AR mRNA levels in T-47D (ER+, PR+) cells 6 hr after treatment, whereas oestradiol (E2) had no effect. In MDA-MB-453 (ER-, PR-) cells, regulation of AR mRNA by RA differed from the other cell lines: RA increased the level of AR mRNA. DHT-binding assays indicated a corresponding increase in AR protein. Transfection of the androgen-responsive mouse mammary tumour virus long-terminal repeat (MMTV LTR) linked to a chloramphenicol acetyltransferase (CAT) reporter gene was used to examine the effect of altered AR levels on androgen action. The increased level of AR following RA pre-treatment in MDA-MB-453 cells resulted in enhanced induction of CAT activity by DHT and, conversely, a decrease in the level of AR following RA pretreatment in T-47D cells resulted in reduced induction of CAT activity by DHT. These data demonstrate that AR is expressed predominantly in ER+ and PR+ cell lines and its expression is regulated by ligands also known to regulate ER or PR, including progestins and retinoids. Androgen responsiveness measured by a transfected reporter gene was altered according to the extent of up- or down-regulation of AR expression, demonstrating that responsiveness is dependent on receptor concentration.
Int J Cancer 1992 Nov 11
PMID:Regulation of androgen receptor gene expression by steroids and retinoic acid in human breast-cancer cells. 142 32


1 2 3 4 5 6 7 8 9 10 Next >>

---