Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Somatostatin is a potent antiproliferative signal in both tumoral and normal mammalian cells, and altered somatostatin receptor (sst) expression is associated with carcinogenesis in human tissues. In this study, two normal and three tumoral human pineal glands were analyzed using the reverse transcriptase-polymerase chain reaction (RT-PCR) for the presence of mRNA coding for the five different somatostatin receptors (sst1-sst5). Pineal parenchymal tumor (PPT) differentiation was confirmed by immunohistochemical detection of neuroendocrine markers (synaptophysin, neurofilaments, and chromogranin A). The presence of mRNA coding for c-myc, a proto-oncogene, and for tryptophan hydroxylase (TPOH), serotonin N-acetyltransferase (NAT), and hydroxyindole-O-methyltransferase (HIOMT), enzymes of the melatonin pathway, was also analyzed by RT-PCR. Only the tumoral tissues contained c-myc mRNA. All five tissues contained TPOH, NAT, and HIOMT mRNA, the levels of HIOMT mRNA being lower in PPT than in the normal pineal gland, suggesting that PPT retain the ability to synthesize melatonin. All tissues contained sst1, sst2, and sst3 transcripts, but not sst4, while small amounts of sst5 mRNA were only found in normal pineal glands. Real-time PCR, performed only with the most abundant subtpe sst2, evidenced an about sixfold higher level in in normal pineal glands. These results demonstrate the presence of somatostatin receptors in the human pineal gland, as described in other species, and point to a differential expression of the sst2 and sst5 subtypes associated with carcinogenesis.
Cell Mol Neurobiol 2003 Feb
PMID:Differential somatostatin receptor subtype expression in human normal pineal gland and pineal parenchymal tumors. 1270 86

By RT-PCR two transcripts for arylalkylamine N-acetyltransferase (AA-NAT; serotonin N-acetyltransferase; EC 2.3.1.87), the key enzyme in melatonin synthesis, were found, for the first time, in the oocytes and blastoderms from freshly laid eggs (323- and 238-bp RT-PCR products), and one (238-bp product) in the pineal gland of Japanese quail (Coturnix coturnix japonica). The two products differed by an intron of 85-bp present in the 323-bp band and absent from the 238-bp band. The identity of the products was confirmed by restriction analysis and sequencing. The ratio of the 323:238-bp bands changed during oogenesis from approximately 17:1 in small 3-mm oocytes to approximately 4:1 in immature vitellogenic oocytes and approximately 1:1 in mature, preovulatory oocytes; it was reversed to approximately 0.2:1 in blastoderms from fertile freshly laid eggs, corresponding to embryo of approximately 40,000 cells. It is proposed that the longer 323-bp product, containing an intron, represents a translationally inactive form of the transcript, stored in maternal RNA. The shorter 238-bp product lacking an intron may represent the mature active AA-NAT mRNA found in the pineal gland and in early embryos, and-to a lower proportion-in older oocytes. These data constitute the first direct proof of an intron sequence in maternal RNA of avian oocyte. It is possible that differential processing of the immature mRNA is part of a transcriptional regulation mechanism of AA-NAT activity. A possible role of extrapineal melatonin in early avian development is discussed.
Mol Reprod Dev 2003 Jun
PMID:Presence and developmental regulation of serotonin N-acetyltransferase transcripts in oocytes and early quail embryos (Coturnix coturnix japonica). 1270 23

Transient and stable gene delivery systems are available for Trichomonas vaginalis, however, they do not allow regulated expression of target genes. To study essential genes or proteins that are toxic to the cells when over expressed, we have developed an inducible/repressible gene expression system in this parasite, which is driven by the tet-operator (tetO) and regulated tetracycline-responsive Tet repressor (TetR). Inducible chloramphenicol acetyl transferase (CAT) gene expression is observed using a concentration of tetracycline (Tc) as low as 0.1 microg x ml(-1). Expression increases with drug dose with a maximum level of CAT induction achieved in stable transfectants using 5 microg x ml(-1) Tc. CAT protein expression is detectable within 12 h and reaches a maximum level at 48 h, demonstrating that inducible expression is time and dose-dependent. In an inverse experiment, parasites previously cultivated with 1 microg x ml(-1) of Tc for 48 h, were grown in the absence of drug to determine the kinetics of repression. A significant decrease in protein concentration is detected after 48 h, and no detectable protein is observed after 72 h. Experiments replacing the CAT gene with the puromycin N-acetyltransferase (PAC) gene in the Tet regulated expression construct have demonstrated the use of this system for testing putative toxic and essential genes. The establishment of regulated gene expression of exogenous genes in T. vaginalis represents a crucial step towards determining the function of proteins in this divergent parasite.
Mol Biochem Parasitol 2003 Apr 25
PMID:Tetracycline-inducible gene expression in Trichomonas vaginalis. 1270 95

Arylalkylamine N-acetyltransferase (NAT) from the female colleterial glands of Periplaneta americana showed activity peaks at pH 6.0 and 9.5 and the pH profile changed during oogenesis. The left gland contained higher activity than the right gland but the right gland also contained recognizable activity. The patterns in activity change depended on the substrate used, tryptamine (TN) or serotonin (5-HT). When TN was used as the substrate, the alkaline peak was higher than the acidic peak. In contrast, when 5-HT was used, the acidic peak was much higher than the alkaline peak. This suggests that at least two NATs are present in this species that are specific to pH and substrate species. Of the four combinations of the two pH ranges and two substrate indolamines, the enzyme activity that showed a similar change to the oocyte maturation was obtained in the combination of pH 6.0 and TN. TN was actually detected in the colleterial glands by fluorescent measurements according to Hess and Uderfriend [J. Pharmacol. Exp., 127 (1959) 175-177]. It peaked on the 6th day of emergence, which corresponded to the first rise of oocyte length and yolk accumulation, whereas a small peak appeared in the phase of the second rise. TN, or more likely N-acetyl TN, may therefore be involved in the regulation of oocyte maturation which could be a novel mechanism in oocyte maturation.
Comp Biochem Physiol A Mol Integr Physiol 2003 Apr
PMID:Multiple forms of arylalkylamine N-acetyltransferase (NAT) from cockroach female colleterial glands and activity changes during oocyte maturation. 1281 88

Genetic regulation of acetyl coenzyme A-dependent N-acetyltransferase (NAT)and O-acetyltransferase (OAT) activities may play an important role in the metabolic activation of arylamine chemicals and carcinogens. N-acetylation is thought to be the first step in arylamine metabolism. The enzyme responsible for N-acetylation is called NAT. In this study, synthetic non-steroidal antiestrogen tamoxifen was selected for determining the inhibition of arylamine NAT activity, gene expression (NAT mRNA) and DNA-2-aminofluorene adduct formation in human leukemia HL-60 cell line. The results demonstrated that tamoxifen did not affect the level of NAT mRNA in HL-60 cells. But the results also showed that NAT activity and 2-Aminofluorene-DNA adduct formation in HL-60 cells were inhibited and decreased by tamoxifen in a dose-dependent manner when the doses of tamoxifen up to 100 micro M. We also examined the standard steady-state kinetic analysis, and the data showed that tamoxifen may be an uncompetitive inhibitor to NAT activity in cytosols based on the decrease apparent values of Km and Vmax. This report is the first finding that tamoxifen inhibited human leukemia HL-60 cells NAT activity and DNA-2-aminofluorene on adduct formation.
Res Commun Mol Pathol Pharmacol 2001
PMID:Tamoxifen inhibits arylamine N-acetyltransferase activity and DNA-2-aminofluorene adduct in human leukemia HL-60 cells. 1288 15

The study reports the change of transcription pattern of serotonin N-acetyltransferase gene and melatonin receptor genes during ontogenesis of the avian pineal gland. The RT-PCR technique was used to investigate the expression of the arylalkylamine N-acetyltransferase (AA-NAT) and melatonin receptor genes during development of the pineal glands isolated from Japanese quail (Coturnix coturnix japonica) embryos incubated from 3 days on until hatching (17 days), and in some organs (pineal, brain hemisphere, eye, leg, heart) of the 3-day-old quail embryo. It was shown that two phases of AA-NAT expression are observed during pineal gland development. The first, embryonic-type phase, lasts from the beginning until 7-10 days of incubation, and is marked by the presence of two RT-PCR products for AA-NAT: the shorter mature form without intron (238 bp), and the longer form (323 bp) containing an unprocessed intron of 85 bp. The second, adult-type phase is characterized by the presence of a single mature transcript, containing no intron; it starts from 7 to 10 days of incubation and lasts until hatching and in the adult pineal. The duration of this transition time from the embryonic to the adult transcription pattern in the quail pineal gland from 7 to 10 days of incubation we attribute to asynchronic embryo development, because quail chicks usually hatch between the 16th and 19th day of incubation. Analysis of the AA-NAT protein sequences for chick and quail (GeneBank accession no. U 46 502 and AF 007 068, respectively) revealed their perfect homology with the part of protein read from the sequence present in the adult-type phase of the pineal gland (the RT-PCR product of 238 bp). The presence of the intron (in the 323 bp RT-PCR product, accession no. AY 197 460) in the embryonic-phase of the pineal gland changes the reading frame of the mRNA sequence and the hypothetical resulting protein loses its homology with the chick and quail AA-NAT enzyme starting with 105th amino acid of the complete chick AA-NAT protein comprising 205 amino acids (accession no. U 46 502). In the whole embryos at stages 1-8 (according to the Hamburger-Hamilton classification) both RT-PCR products with and without intron were consistently found, and individual tissues from 3-day-old embryos also produced two AA-NAT products, i.e., the expression was of the embryonic-type. At the time of transition from the embryonic to the adult AA-NAT transcription pattern, in 7-11-day-old embryos, all three melatonin receptor transcripts (mel-1a, mel-1b, and mel-1c) were observed in the pineals, without consistent modifications of the band intensity. In the adult pineal, a single mature AA-NAT transcript was present as well as all three melatonin receptor transcripts, usually with preferential expression of the mel-1a band. The transition time from the embryonic to adult AA-NAT expression pattern coincides well with the acquisition of functional activity and the appearance of melatonin synthesis in the embryonic pineal reported for chicken, as related to quail. We suggest that the change in transcription pattern of the AA-NAT gene may reflect another, still unknown mechanism of regulating AA-NAT activity during ontogenesis, at the level of mRNA processing, whose specificity (or not) for embryonic development we wish to establish in the future.
Mol Reprod Dev 2004 Feb
PMID:Transition from embryonic to adult transcription pattern of serotonin N-acetyltransferase gene in avian pineal gland. 1469 29

Acetyl CoA:arylamine N-acetyltransferase (NAT) enzymes catalyze the N-acetylation of aromatic amines and the O-acetylation of aryl hydroxylamines, reactions that govern the disposition and toxicity of many drugs and carcinogens. The human NAT genes and enzymes NAT1 and NAT2 are highly polymorphic and constitute one of the best studied examples of the genetic control of drug metabolism. Naturally occurring human NAT variants provide limited insight into the relationship between NAT amino acid sequence and enzyme activity. We have shown previously that the expression of recombinant NAT2 in bacterial tester strains results in greatly enhanced sensitivity to mutagenic nitroaromatic compounds (which are reduced to aryl hydroxylamines by bacterial enzymes). We hypothesized that random mutagenesis combined with rapid screening could be used to identify functionally significant amino acid residues in NAT enzymes. Pools of NAT2 variants were generated by polymerase chain reaction-mediated random mutagenesis of the complete coding sequence. Reversion induced by a NAT-dependent mutagen, 3-methyl-2-nitroimidazo[4,5-f]quinoline, was used as the basis for screening these pools to identify variants with altered enzyme activity. Eighteen variants were characterized by quantitative mutagenicity assays and enzyme kinetic measurements. This approach can provide new insight into the biochemistry of enzymes involved in the metabolic activation of mutagens.
Mol Pharmacol 2004 Jan
PMID:Human acetyl CoA:arylamine N-acetyltransferase variants generated by random mutagenesis. 1472 54

Pineal function is defined by a set of very narrowly expressed genes that encode proteins required for photoperiodic transduction and rhythmic melatonin secretion. One of these proteins is serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT), which controls the daily rhythm in melatonin production. Here, pineal-specific expression of the zebrafish aanat-2 (zfaanat-2) was studied using in vivo transient expression analyses of promoter-reporter constructs; this revealed that specificity is determined by two regions located 12 kb away from each other. One is the 5'-flanking region, and the other is a 257-bp sequence, located 6 kb downstream of the transcribed region. This 3'-sequence, designated pineal-restrictive downstream module (PRDM), has a dual function: enhancement of pineal expression and inhibition of extrapineal expression. The former is an autonomic property of PRDM whereas the later function requires interaction with the upstream regulatory region of zfaanat-2. Functional analyses of the PRDM sequence revealed that three photoreceptor conserved elements (TAATC) and a single perfect E-box (CACGTG) are crucial for the dual function of PRDM. These results indicate that pineal specificity of zfaanat-2 is determined by the dual functionality of the PRDM and the interaction between upstream regulatory region and downstream photoreceptor conserved elements and E-box element.
Mol Endocrinol 2004 May
PMID:Zebrafish serotonin-N-acetyltransferase-2 gene regulation: pineal-restrictive downstream module contains a functional E-box and three photoreceptor conserved elements. 1498 31

The nocturnal biosynthesis of melatonin in the rat pineal depends on strongly enhanced expression of the enzyme N-acetyltransferase [arylalkylamine N-acetyltransferase (AA-NAT); EC 2.3.1.87]. AA-NAT transcription is stimulated during darkness by adrenergic inputs to the pineal from the suprachiasmatic nucleus (SCN). Nocturnal activation of the AA-NAT promotor following stimulation of pinealocyte adrenoceptors involves cAMP-dependent stimulation of protein kinase A (PKA). The nocturnal rise in AA-NAT depends on the lighting conditions. As compared with light/dark (LD) 12:12, the delay between dark onset and the nocturnal rise in AA-NAT is shortened under long photoperiods and prolonged under short photoperiods. Here, we report that the rapidity of nocturnal AA-NAT induction depends on cAMP inducibility of the gene. Accordingly, cAMP produces a strong AA-NAT response in pineals obtained from rats housed under long photoperiods and a weak AA-NAT response under short photoperiods. Changes in AA-NAT inducibility are fully developed not earlier than after seven cycles. This observation suggests that long-term changes in the photoperiod are necessary to achieve full adjustment of cAMP inducibility of the gene. A direct relationship was found between cAMP-dependent AA-NAT inducibility and the pineal protein kinase A (PKA) activity. As compared to LD 12:12, PKA activity was increased under LD 20:4 and attenuated under LD 4:20. On the basis of the present findings, we suggest that the photoperiod determines the effectiveness of nocturnal AA-NAT induction by long-term modulation of the intrapineal pathway that transmits the cAMP signal to the AA-NAT gene.
Brain Res Mol Brain Res 2004 Apr 07
PMID:Rat pineal arylalkylamine-N-acetyltransferase: cyclic AMP inducibility of its gene depends on prior entrained photoperiod. 1504 65

Coffee drinking has been associated with reduced incidence of colorectal cancer, possibly via chemoprotection/modification of the metabolism of dietary heterocyclic amine carcinogens such as 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP) by kahweol and cafestol palmitates (K/C), two components of unfiltered coffee. Using the PhIP-exposed male Fisher F344 rat as a model, K/C have been shown to reduce colonic PhIP-DNA adducts by > 50%. We have used the male F344 rat to investigate the effects of dietary K/C (0.02-0.2% as a 1:1 mixture) on the metabolism of PhIP by N-acetyltransferase- (NAT), sulfotransferase- (SULT), and glutathione-dependent pathways. K/C decreased hepatic NAT-dependent PhIP activation by up to 80% in a dose-dependent manner. Conversely, hepatic glutathione S-transferase (GST) activity/expression increased, e.g., 3-4 fold toward 1-chloro-2,4-dinitrobenzene (total activity), up to 23-fold toward 4-vinylpyridine (rGSTP1), and approximately 7-fold for rGSTA2 protein. These effects had fully developed after 5 days of the test diet and persisted for at least 5 days after withdrawal of K/C. Hepatic glutathione increased two- to threefold and this increase was more short-lived than other changes. K/C did not modify hepatic SULT activity or colon NAT and GST activities. Benzylisothiocyanate and black tea, which have also been shown to reduce the formation of PhIP-DNA adducts in this model, had little effect on hepatic NAT, SULT, GST, or GSH. In primary culture of rat hepatocytes, both kahweol and cafestol palmitates reduced NAT activity by 80%. In summary, the unique potential of K/C to convert rapid acetylators to a slow acetylator phenotype, accompanied by GST induction, might contribute to chemoprevention against cancers associated with heterocyclic amines.
Environ Mol Mutagen 2004
PMID:Potential chemoprotective effects of the coffee components kahweol and cafestol palmitates via modification of hepatic N-acetyltransferase and glutathione S-transferase activities. 1546 54


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