PubMed Health⌕ Search

Biomedical subjects

Y Qian

Publications and source records attributed to Y Qian.

At least 163 records · Page 9Linked to original sources
PubMed1998

Phosphorylation and regulation of antidepressant-sensitive serotonin transporters.

Antidepressant-sensitive serotonin (5-hydroxytryptamine, 5HT) transporters (SERTs) are responsible for efficient synaptic clearance of extracellular 5HT. Previously (Qian, Y., Galli, A., Ramamoorthy, S., Risso, S., DeFelice, L. J., and Blakely, R. D. (1997) J. Neurosci. 17, 45-47), we demonstrated that protein kinase (PKC)-linked pathways in transfected HEK-293 cells lead to the internalization of cell-surface human (h) SERT protein and a reduction in 5HT uptake capacity. In the present study, we report that PKC activators rapidly, and in a concentration-dependent manner, elevate the basal level of hSERT phosphorylation 5-6-fold. Similarly, protein phosphatase (PP1/PP2A) inhibitors down-regulate 5HT transport and significantly elevate hSERT 32P incorporation, effects that are additive with those of PKC activators. Moreover, hSERT phosphorylation induced by beta-phorbol 12-myristate 13-acetate is abolished selectively by the PKC inhibitors staurosporine and bisindolylmaleimide I, whereas hSERT phosphorylation induced by phosphatase inhibitors is insensitive to these agents at comparable concentrations. Protein kinase A and protein kinase G activators fail to acutely down-regulate 5HT uptake but significantly enhance hSERT phosphorylation. Basal hSERT and okadaic acid-induced phosphorylation were insensitive to chelation of intracellular calcium and Ca2+/calmodulin-dependent protein kinase inhibitors. Together these results reveal hSERT to be a phosphoprotein whose phosphorylation state is likely to be tightly controlled by multiple kinase and phosphatase pathways that may also influence the transporter's regulated trafficking.

Carrier Proteins↗
PubMed1998

Glutathione levels are reduced in diabetic rat retina but are not influenced by ischemia followed by recirculation.

Free radicals have recently been proposed to play a role in the development of diabetic retinopathy. The aim of the present study was to examine whether the abnormal metabolism caused by diabetes and by ischemia followed by recirculation interferes with a free radical enzyme defense system in the retina, ie, glutathione. Diabetes mellitus was induced by injecting streptozotocin ([STZ] 60 mg/kg body weight [BW] intraperitoneally). After 2 and 6 months, respectively, glutathione levels were measured in the retina and compared against those of age-matched normal control rats. Retinal ischemia was induced by careful ligation of the vessels and the accompanying optic nerve behind the left eye bulb. The right eye served as a control. After 90 minutes of ischemia, retinal circulation was reestablished by removing the ligature. Two-month-old diabetic rats were kept for an additional 3 days and normal rats for 5 minutes, 15 minutes, or 3 days before they were killed for measurement of glutathione. Retinal levels of glutathione were significantly lower in 6-month diabetic compared with 2-month diabetic rats (16.6 +/- 2.9 v 19.0 +/- 2.2 nmol/mg protein, P < .05) and 6-month normal control rats (16.6 +/- 2.9 v 21.0 +/- 2.1 nmol/mg protein, P < .001). Ischemia followed by recirculation did not influence the total tissue level of glutathione either in 2-month-old diabetic rats or in normal rats. The present study indicates that the abnormal metabolism caused by diabetes, rather than by changes in retinal circulation, results in an impaired defense mechanism against free radicals, a factor that may be of importance for the development of diabetic retinopathy. However, since glutathione levels in the present study were measured in the whole retina, it cannot be excluded that particular cell types, such as vascular cells, show an alteration in glutathione that is masked by the glutathione levels in the other nonvascular cells of the retina. Studies using other techniques are needed to further explore this subject.

Animals↗
PubMed1998

Kinetics of biodegradation of di-n-butyl phthalate in continuous culture system.

The characteristics of microbial growth and kinetics of DBP biodegradation was studied in a continuous culture system using DBP as a sole source of carbon. The results showed that, at high substrate concentration, the microbial growth was inhibited by DBP, and can be described by the Haldane model. Kinetic parameters based on Haldane substrate inhibition were evaluated. The values were mu(m) = 0.38 h-1, Ki = 86 mg/l, Ks = 28 mg/l. The DBP concentration to avoid substrate inhibition was inferred theoretically and determined to be 49 mg/L.

Biodegradation, Environmental↗
PubMed1998

Tuberculosis control through respirator wear: performance of National Institute for Occupational Safety and Health-regulated respirators.

BACKGROUND: In 1995 the National Institute for Occupational Safety and Health issued new rules for personal respirators. All nine new respirator categories are authorized in health care facilities for the prevention of the transmission of tuberculosis (TB). The new N95 respirator category is the most frequently used for this purpose. Data are presented on their efficiency for collecting TB-size bacteria and their potential for reaerosolizing collected bacteria. METHODS: All measurements of bacterial penetration were performed with dynamic aerosol size spectrometers at flow conditions corresponding to normal wear and respirator certification conditions. The reaerosolization tests were performed at conditions ranging from normal breathing to violent coughing or sneezing. RESULTS: The tested N95 respirators collected 0.1 to 0.3 microm particles with efficiencies of 95% or higher, as specified by the regulations. TB-size bacteria of 0.8 microm and larger, however, were collected with 99.5% or higher efficiencies; that is, the penetration of these bacteria through the filter material was 0.5% or less, much less than the required maximum penetration of 5% for the smaller particle sizes. No bacteria were reaerosolized during normal exhalation. Some reaerosolization (0.1% or less) was observed only at low humidity and extremely high air flow through the respirator, corresponding to violent coughing or sneezing. CONCLUSIONS: The filter materials of N95 respirators provide good protection against TB bacteria. Thus, a significant number of bacteria can enter the respirator-wearer's breathing space only through spaces where the respirator inadequately seals to the wearer's face. Reentrainment and reaerosolization of mycobacteria is not a problem when normal work practices are observed in health care facilities.

Equipment Contamination↗
PubMed1998

Prostaglandin E2 in the salivary glands of the female tick, Amblyomma americanum (L.): calcium mobilization and exocytosis.

A cholera toxin-sensitive, prostaglandin E2 (PGE2) specific receptor has been identified in the plasma membrane fraction of tick salivary glands. In the present study, we report that stimulation of dispersed salivary glands of the lone star tick Amblyomma americanum (L.) with 1 nM to 10 microM PGE2 increased the intracellular concentration of inositol trisphosphate (IP3) in a dose-dependent manner. Incubation of dispersed tissue with 1 nM to 10 microM PGE2 also stimulated release of 45Ca2+ from preloaded tissue. PGE2 (10 microM) did not stimulate an influx of 45Ca2+. Therefore, the PGE2 receptor in the salivary glands appears to activate a phosphoinositide phospholipase C signalling pathway to increase formation of intracellular IP3 and, thus, mobilize Ca2+ from intracellular stores. Incubation of dispersed salivary glands with 1 nM to 1 microM PGE2 stimulated secretion of anticoagulant protein, but not at < 1 nM or > 1 microM PGE2. In addition, the mammalian PGE2 EP1 receptor antagonist AH-6809 affected secretion of anticoagulant by dispersed salivary gland tissue at a low concentration supporting the hypothesis that the PGE2 receptor in tick salivary glands is EP1-like. We propose that a major function for PGE2 in tick salivary glands is to mobilize Ca2+ and stimulate secretion (exocytosis) of bioactive proteins into the tick's saliva during feeding.

Animals↗
PubMed1998

Selective inhibition of type-I geranylgeranyltransferase in vitro and in whole cells by CAAL peptidomimetics.

In this paper we describe the synthesis of a family of CAAL peptidomimetics as GGTase-I inhibitors. These inhibitors lack the central dipeptide AA in the key CAAL carboxy terminal sequence of geranylgeranylated proteins and are more selective for GGTase-I over FTase. In whole cells, these compounds are very potent inhibitors of the processing of the geranylgeranylated protein Rap1A without affecting the farnesylated protein H-Ras. One derivative, GGTI-298, inhibited cell division by blocking cells in the G1 phase of the cell cycle.

3T3 Cells↗
PubMed1998

Intron function in the nonsense-mediated decay of beta-globin mRNA: indications that pre-mRNA splicing in the nucleus can influence mRNA translation in the cytoplasm.

Generally, mRNAs that prematurely terminate translation are abnormally low in abundance. In the case of mammalian cells, nonsense codons most often mediate a reduction in the abundance of newly synthesized, nucleus-associated mRNA by a mechanism that is not well understood. With the aim of defining cis-acting sequences that are important to the reduction process, the effects of particular beta-globin gene rearrangements on the metabolism of beta-globin mRNAs harboring one of a series of nonsense codons have been assessed. Results indicate that nonsense codons located 54 bp or more upstream of the 3'-most intron, intron 2, reduce the abundance of nucleus-associated mRNA to 10-15% of normal without altering the level of either of the two introns within pre-mRNA. The level of cytoplasmic mRNA is also reduced to 10-15% of normal, indicating that decay does not take place once the mRNA is released from an association with nuclei into the cytoplasm. A nonsense codon within exon 2 that does not reduce mRNA abundance can be converted to the type that does by (1) inserting a sufficiently large in-frame sequence immediately upstream of intron 2 or (2) deleting and reinserting intron 2 a sufficient distance downstream of its usual position. These findings indicate that only those nonsense codons located more than 54 bp upstream of the 3'-most intron reduce beta-globin mRNA abundance, which is remarkably consistent with which nonsense codons within the triosephosphate isomerase (TPI) gene reduce TPI mRNA abundance. We propose that the 3'-most exon-exon junction of beta-globin mRNA and, possibly, most mRNAs is marked by the removal of the 3'-most intron during pre-mRNA splicing and that the "mark" accompanies mRNA during transport to the cytoplasm. When cytoplasmic ribosomes terminate translation more than 54 nt upstream of the mark during or immediately after transport, the mRNA is subjected to nonsense-mediated decay. The finding that deletion of beta-globin intron 2 does not appreciably alter the effect of any nonsense codon on beta-globin mRNA abundance suggests that another cis-acting sequence functions in nonsense-mediated decay comparably to intron 2, at least in the absence of intron 2, possibly as a fail-safe mechanism. The analysis of deletions and insertions indicates that this sequence resides within the coding region and can be functionally substituted by intron 2.

Biological Transport↗
PubMed1998

Sequence of a Menkes-type Cu-transporting ATPase from rat C6 glioma cells: comparison of the rat protein with other mammalian Cu-transporting ATPases.

Rat Atp7a occupied a single open reading frame (274502) which coded for a protein of 1492 residues. Rat Atp7a was 98% and 95% identical to published sequences for the mouse and Chinese hamster, respectively, and 94% homologous to human ATP7A. Compared to ATP7A, the rat transcript coded for an additional alanine (A446) in the heavy metal binding (Hmb) domain and showed a 34 bp gap in the 3' UTR. Based on published sequence data, hydropathic profiles for rat, mouse, Chinese hamster, and human Cu-ATPases were practically identical with the exception of 8 additional amino acid residues between the 4th and 5th Hmb sites in the human. As deduced from amino acid sequence data, Hmb was predicted to have regions with helical and beta structures. All four species had five of the six metal binding sites centered within hydrophobic regions. The comparative analyses suggested that the Hmb region of the molecule could experience numerous amino acid substitutions with no apparent disruption to theATPase transport function whereas variations to theATPase domain would be more critical.

Adenosine Triphosphatases↗
PubMed1998

Both farnesyltransferase and geranylgeranyltransferase I inhibitors are required for inhibition of oncogenic K-Ras prenylation but each alone is sufficient to suppress human tumor growth in nude mouse xenografts.

The ability of Ras oncoproteins to cause malignant transformation requires their post-translational modifications by prenyl groups. Because K-Ras can be both farnesylated and geranylgeranylated it is not known whether both farnesyltransferase and geranylgeranyltransferase I inhibitors are required for suppressing human tumor growth in whole animals. In this paper we report that oncogenic Ras processing, MAP kinase activation and growth in nude mice are inhibited by the farnesyltransferase inhibitor FTI-276 in H- and N-Ras transformed NIH3T3 cells; whereas in KB-Ras transformed NIH3T3 cells both FTI-276 and the geranylgeranyltransferase I inhibitor GGTI-297 are required for inhibition. Furthermore, human lung A-549 and Calu-1 carcinoma cell lines were found to co-express H-, N- and K-Ras. In Calu-1 cells, the processing of H- and N-Ras is inhibited greatly by FTI-276 but only partially by GGTI-297 whereas K-Ras processing inhibition requires both FTI-276 and GGTI-297. In contrast, in A-549 cells the processing of H- and N-Ras is inhibited only by FTI-276 and K-Ras processing is resistant to co-treatment with FTI-276 and GGTI-297. Yet, the growth in nude mice of A-549 and Calu-1 xenografts, both of which express K-Ras mutations, is inhibited by FTI-276 (80% inhibition) and GGTI-297 (60%). Furthermore, FTI-276 inhibits tumor growth of NIH3T3 cells transformed by a form of oncogenic H-Ras that is exclusively geranylgeranylated and whose processing is resistant to this inhibitor. Taken together, the results demonstrate that both FTase and GGTase I inhibitors are required for inhibition of K-Ras processing but that each alone is sufficient to suppress human tumor growth in nude mice.

3T3 Cells↗
PubMed1998

The glutathione levels are reduced in Goto-Kakizaki rat retina, but are not influenced by aminoguanidine treatment.

PURPOSE: To examine the levels of the free radical protecting enzyme glutathione and the endothelial/pericyte ratio in retinal capillaries in the Goto-Kakizaki (GK) Wistar rat, with and without aminoguanidine treatment. METHODS: Eight-month-old GK rats, with non-obese, spontaneous non-insulin-dependent diabetes mellitus (NIDDM), were examined after a six month period of aminoguanidine treatment. Glutathione levels were measured with high performance liquid chromatography and the endothelial/pericyte ratio was calculated in trypsin digested vessel preparations. RESULTS: The levels of glutathione in GK rat retina were significantly lower compared to controls (p = 0.0108). There was no difference in the endothelial/pericyte ratio compared to matched control rats (1.8 +/- 0.2 vs. 1.8 +/- 0.1, respectively). Aminoguanidine treatment did not influence either the degree of hyperglycemia, the levels of glutathione or the endothelial/pericyte ratio in GK or control rat retina. CONCLUSIONS: The results indicate that impaired glucose metabolism may influence one of the defense mechanisms for oxidative stress, but also suggest that decreased glutathione levels occur prior to morphological signs of pericyte loss and/or endothelial cell proliferation in this animal model of hereditary NIDDM.

Animals↗
PubMed1998

Method for measuring the spatial variability of aerosol penetration through respirator filters.

Fibrous filter media are widely used in respirators to remove airborne particulate matter from the inhaled airflow of workers. The N95 half-mask particulate respirator appears to be the most frequently used respirator under the new NIOSH regulation, 42 CFR 84. Considerable spatial variability in light penetration through the fibrous filter medium of an N95 respirator can be seen by visual observation when it is held to the light. This variability is due to the way in which the fibers are manufactured and laid down to form the filter medium. Similar spatial variability is expected in the aerosol penetration through the filters. Therefore, a test method has been developed for measuring the spatial variability in aerosol penetration. The main components of this method are an aerosol generator, a filter test stand with a movable sampling inlet, an aerosol size spectrometer, and an aerosol photometer. Measurements with the filter media of N95 respirators, tested at average filtration velocities corresponding to light, moderate, and heavy work loads, have shown spatial variations in aerosol penetration in excess of 100% relative to the average aerosol penetration for the entire respirator. N95 respirators are required to be at least 95% efficient (i.e., less than 5% penetrating) at the most penetrating particle size, when tested at 85 L/min. Tests with the new method have shown that the aerosol penetration of the most penetrating particles of about 0.1 micron diameter may locally be higher than 5%, while the average aerosol penetration of 0.1 micron particles is less than 5%.

Aerosols↗
PubMed1998

Performance of N95 respirators: filtration efficiency for airborne microbial and inert particles.

In 1995 the National Institute for Occupational Safety and Health issued new regulations for nonpowered particulate respirators (42 CFR Part 84). A new filter certification system also was created. Among the new particulate respirators that have entered the market, the N95 respirator is the most commonly used in industrial and health care environments. The filtration efficiencies of unloaded N95 particulate respirators have been compared with those of dust/mist (DM) and dust/fume/mist (DFM) respirators certified under the former regulations (30 CFR Part 11). Through laboratory tests with NaCl certification aerosols and measurements with particle-size spectrometers, N95 respirators were found to have higher filtration efficiencies than DM and DFM respirators and noncertified surgical masks. N95 respirators made by different companies were found to have different filtration efficiencies for the most penetrating particle size (0.1 to 0.3 micron), but all were at least 95% efficient at that size for NaCl particles. Above the most penetrating particle size the filtration efficiency increases with size; it reaches approximately 99.5% or higher at about 0.75 micron. Tests with bacteria of size and shape similar to Mycobacterium tuberculosis also showed filtration efficiencies of 99.5% or higher. Experimental data were used to calculate the aerosol mass concentrations inside the respirator when worn in representative work environments. The penetrated mass fractions, in the absence of face leakage, ranged from 0.02% for large particle distributions to 1.8% for submicrometer-size welding fumes. Thus, N95 respirators provide excellent protection against airborne particles when there is a good face seal.

Aerosols↗
PubMed1998

Functional analysis of copper homeostasis in cell culture models: a new perspective on internal copper transport.

The movement of copper ions across membrane barriers of vital organs and tissues is a priority topic in nutrition and one for which there continues to be little understanding of the mechanism. Reports of membrane-bound, copper-transporting adenosine triphosphatases (Cu-ATPases) selective for copper ions have brought new focus to the problem and prompted fresh ideas. Using a cell culture model approach, we attempted to learn whether transport into and out of cells depends on a Cu-ATPase. Measurement of transport kinetics in fibroblasts, brain glial cells, neuroblastoma cells, and placental cells showed differences in the rates of copper uptake and response to sulfhydryl reagents. BeWo cells, a human choriocarcinoma placental cell line, behaved as did Menkes fibroblasts by avidly absorbing copper but not releasing copper to the immediate environment. Further tests showed that BeWo cells did not express the transcript for the membrane-bound Cu-ATPase that has been identified with Menkes syndrome. Transcript induction, however, was achieved by growing BeWo cells on porous filters that allowed apical and basolateral surfaces to form. With transcript expression, the cells showed a capacity to release copper into the medium. BeWo cells also synthesized a form of ceruloplasmin whose structure differed from that of the plasma protein and hence may be a product of a different gene. BeWo cells may also express the gene for Wilson disease, thus linking Menkes and Wilson proteins to maternal delivery of copper. We constructed a model in which both ATPases work in concert in a vesicle-based transport mechanism. The vesicle model may help us understand the transport of copper across the placenta and all cells in general.

Adenosine Triphosphatases↗
PubMed1998

Copper efflux from murine microvascular cells requires expression of the menkes disease Cu-ATPase.

Previously, we showed that the transport of Cu by PC12 pheochromocytoma cells and C6 glioma cells correlated with the expression of a Cu-transporting ATPase (Atp7a) that has been linked to Menkes disease. Here, we show that cerebrovascular endothelial (CVE) cells that comprise the blood-brain barrier (BBB) also express the gene for the Cu-ATPase. By using reverse transcription-polymerase chain reaction (RT-PCR) and primers designed from mouse Atp7a cDNA, we amplified a 925-bp and a 760-bp cDNA fragment from two extreme regions of Atp7a mRNA from murine CVE cells; 777 bp of the 925-bp fragment and 677 bp of the 760-bp fragment had a 99.7 and 100% sequence homology, respectively, with mouse Atp7a cDNA. The 777-bp sequences covered the heavy metal binding (Hmb) domain and the 677-bp fragment coded for residues at the -COOH terminus of Atp7a. A functional analysis showed that Cu efflux was blocked by the sulfhydryl reagent p-chloromercuribenzoate (p-CMB), a potential inhibitor of Atp7a function. This study provides strong evidence that a Cu-ATPase in the BBB controls the penetration of Cu into the brain and that lesions to the Cu-ATPase in CVE cells are a primary cause of low brain Cu levels in Menkes disease.

Adenosine Triphosphatases↗
PubMed1998

Human NK cell and ADCC reactivity against xenogeneic porcine target cells including fetal porcine islet cells.

In vitro studies of human NK cell-mediated cytotoxicity and ADCC against porcine target cells were performed. Stimulation of human PBMC responder cells with either allogeneic or xenogeneic porcine cells led to a marked increase in NK cell reactivity. Maximum reactivity was reached following 3-6 days of in vitro culture. The sensitivity of target cells ranked as follows: K562 > porcine PHA-induced lymphoblasts > resting porcine PBMC. Limiting dilution analysis showed that allo- and xeno-stimulation in vitro led to differentiation of similar frequencies of effector NK cells. Split culture experiments showed that single NK effector cells were cytotoxic against both K562 and porcine lymphoblasts, demonstrating that individual NK cells lack species specificity. NK effector cell generation stimulated by xenogeneic cells was cyclosporin A (CsA) sensitive and dependent on the presence of autologous responder T lymphocytes, a dependence that was completely reconstituted by the sole addition of human IL-2. Xenostimulation of enriched CD3+ cells also led to a preferential appearance of CD16+ or CD56+ lymphoblasts. Natural xenoreactive human anti-porcine antibodies are mainly of IgM and IgG2 subclasses, but antibodies in xenoimmunised patients reactive against porcine lymphocytes and fetal porcine islet cells were also of IgG1 and IgG3 subclasses. The same subclass distribution was found among antibodies specific for gal(alpha)1,3 gal epitopes as shown by tests performed with alpha1,3 galactosyltransferase-transfected Raji cells (human Burkitt lymphoma cells). Natural antibodies did not mediate ADCC, whereas gal(alpha)1,3 gal-specific antibodies in sera from xenoimmunised patients did. Fetal porcine islet cells were sensitive to human NK cell-mediated cytotoxicity and to ADCC mediated by xenoimmune sera.

Animals↗
PubMed1998

Expression of glnB and a glnB-like gene (glnK) in a ribulose bisphosphate carboxylase/oxygenase-deficient mutant of Rhodobacter sphaeroides.

In a ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO)-deficient mutant of Rhodobacter sphaeroides, strain 16PHC, nitrogenase activity was derepressed in the presence of ammonia under photoheterotrophic growth conditions. Previous studies also showed that reintroduction of a functional RubisCO and Calvin-Benson-Bassham (CBB) pathway suppressed the deregulation of nitrogenase synthesis in this strain. In this study, the derepression of nitrogenase synthesis in the presence of ammonia in strain 16PHC was further explored by using a glnB::lacZ fusion, since the product of the glnB gene is known to have a negative effect on ammonia-regulated nif control. It was found that glnB expression was repressed in strain 16PHC under photoheterotrophic growth conditions with either ammonia or glutamate as the nitrogen source; glutamine synthetase (GS) levels were also affected in this strain. However, when cells regained a functional CBB pathway by trans complementation of the deleted genes, wild-type levels of GS and glnB expression were restored. Furthermore, a glnB-like gene, glnK, was isolated from this organism, and its expression was found to be under tight nitrogen control in the wild type. Surprisingly, glnK expression was found to be derepressed in strain 16PHC under photoheterotrophic conditions in the presence of ammonia.

Artificial Gene Fusion↗
PubMed1998

p21(WAF1/CIP1) is upregulated by the geranylgeranyltransferase I inhibitor GGTI-298 through a transforming growth factor beta- and Sp1-responsive element: involvement of the small GTPase rhoA.

We have recently reported that the geranylgeranyltransferase I inhibitor GGTI-298 arrests human tumor cells at the G1 phase of the cell cycle and increases the protein and RNA levels of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1). Here, we show that GGTI-298 acts at the transcriptional level to induce p21(WAF1/CIP1) in a human pancreatic carcinoma cell line, Panc-1. This upregulation of p21(WAF1/CIP1) promoter was selective, since GGTI-298 inhibited serum responsive element- and E2F-mediated transcription. A functional analysis of the p21(WAF1/CIP1) promoter showed that a GC-rich region located between positions -83 and -74, which contains a transforming growth factor beta-responsive element and one Sp1-binding site, is sufficient for the upregulation of p21(WAF1/CIP1) promoter by GGTI-298. Electrophoretic mobility shift assays showed a small increase in the amount of DNA-bound Sp1-Sp3 complexes. Furthermore, the analysis of Sp1 transcriptional activity in GGTI-298-treated cells by using GAL4-Sp1 chimera or Sp1-chloramphenicol acetyltransferase reporter revealed a significant increase in Sp1-mediated transcription. Moreover, GGTI-298 treatment also resulted in increased Sp1 and Sp3 phosphorylation. These results suggest that GGTI-298-mediated upregulation of p21(WAF1/CIP1) involves both an increase in the amount of DNA-bound Sp1-Sp3 and enhancement of Sp1 transcriptional activity. To identify the geranylgeranylated protein(s) involved in p21(WAF1/CIP1) transcriptional activation, we analyzed the effects of the small GTPases Rac1 and RhoA on p21(WAF1/CIP1) promoter activity. The dominant negative mutant of RhoA, but not Rac1, was able to activate p21(WAF1/CIP1). In contrast, constitutively active RhoA repressed p21(WAF1/CIP1). Accordingly, the ADP-ribosyl transferase C3, which specifically inhibits Rho proteins, enhanced the activity of p21(WAF1/CIP1). Taken together, these results suggest that one mechanism by which GGTI-298 upregulates p21(WAF1/CIP1) transcription is by preventing the small GTPase RhoA from repressing p21(WAF1/CIP1) induction.

Alkyl and Aryl Transferases↗