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S Deb

Publications and source records attributed to S Deb.

At least 73 records · Page 4Linked to original sources
PubMed1996

Transcriptional activation of the human epidermal growth factor receptor promoter by human p53.

The human epidermal growth factor receptor (EGFR) promoter is activated by both wild-type and tumor-derived mutant p53. In this communication, we demonstrate that EGFR promoter sequence requirements for transactivation by wild-type and mutant p53 are different. Transient-expression assays with EGFR promoter deletions identified a wild-type human p53 response element, 5'-AGCTAGACGTCCGGGCAGCCCCCGGCG -3', from positions --265 to --239. Electrophoretic mobility shift analysis and DNase I footprinting assays indicated that wild-type p53 binds sequence specifically to the response element. Using circularly permuted DNA fragments containing the p53-binding site, we show that wild-type p53 binding induces DNA bending at this site. We further show that the EGFR promoter is also activated by tumor-derived p53 mutants p53-143A, p53-175H, p53-248W, p53-273H, and p53-281G. However, the transactivation by mutant p53 does not require the wild-type p53-binding site. The minimal EGFR promoter from positions --104 to --20 which does not contain the wild-type p53-binding site is transactivated by the p53 mutants but not by the wild-type protein, showing a difference in the mechanism of transactivation by wild-type and mutant p53. Transactivation of the EGFR promoter by p53 may represent a novel mechanism of cell growth regulation.

Amino Acid Sequence↗
PubMed1995

The MDR1 downstream promoter contains sequence-specific binding sites for wild-type p53.

We have examined the interaction of the wild-type p53 protein with the downstream promoter of the human multidrug resistance gene-1 (MDR1). Our findings indicate that wild-type p53 inhibits reporter activity driven by the MDR1 downstream promoter (base pairs -189 to +133 relative to the major transcriptional initiation site) in a dose-dependent manner in cotransfection assays in the BHK and the Saos-2 cell lines. A 123 base-pair segment of DNA (-119 to +4 relative to the major transcriptional initiation site), a 193 base-pair segment (-189 to +4), and a 135 base-pair segment (-2 to +133) have been isolated from the MDR1 downstream promoter which, like the full promoter, are negatively controlled by wild-type p53. In addition, we show sequence-specific binding of wild-type p53 protein to the MDR1 downstream promoter. These in vitro results suggest that the presence of wild-type p53 negatively affects expression of the MDR1 gene product, p-glycoprotein, at the transcriptional level.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

N-terminal 130 amino acids of MDM2 are sufficient to inhibit p53-mediated transcriptional activation.

The human oncoprotein MDM2 binds with the tumor suppressor p53 and inhibits p53-directed transactivation. In this report we show that deletion of 336 amino acids from the C-terminus of human MDM2 does not decrease its efficiency to bind p53 in vivo and inhibit p53-directed transactivation. Even further deletion of MDM2 from the C-terminus up to amino acid 131 does not reduce its ability to inhibit p53-mediated transactivation. Since deletion up to amino acid 131 also deletes many antigenic sites of MDM2 and the truncated protein cannot be immunoprecipitated by the antibodies available to us, two internal deletions were made to define the p53-interaction domain. Internal deletion of four amino acids beginning at 110 residue (amino acids 110 to 113) did not reduce p53-binding or inhibition of p53-directed transactivation whereas internal deletion of amino acids 60 to 65 reduces but does not abolish these activities. Sequential deletion of amino acids from the N-terminus leads to sequential destruction of p53-binding and inhibition of transactivation capability of MDM2. Fourteen amino acids can be deleted from this end without any reduction of these activities. Deletion of 28 N-terminal amino acids residues drastically reduces, but does not abolish the p53-binding ability of the protein, as well as inhibition of p53-directed transactivation. Deletion of 58 amino acids from the N-terminus of the oncoprotein abolishes its ability to bind p53 in vivo and to inhibit p53-directed transactivation. These results locate the p53-binding domain of MDM2 within amino acids 14 to 154 and inhibition of transactivation domains of MDM2 within amino acid residues 14 to 130 suggesting possible p53-independent biological functions of the 491 amino acid long oncoprotein.

Humans↗
PubMed1995

Water absorption characteristics of modified hydroxyapatite bone cements.

Water absorption characteristics of a range of modified hydroxyapatite (HA)-reinforced poly(ethyl methacrylate)-n-butyl methacrylate (PEMA-nBMA) bone cements have been established. From gravimetric measurements, the kinetics of successive absorption and desorption cycles, equilibrium uptake, diffusion coefficients and solubility data have been determined. In general, the water uptake could be modelled by the classical laws of diffusion. The introduction of the HA reduced the water uptake of the bone cement, with a further decrease if the HA filler was surface treated with a silane coupling agent. However, the system comprising the silicated silanated HA-filled cement produced a large uptake of water, with relatively low diffusion coefficients, which is attributed to the presence of soluble sites in the matrix.

Absorption↗
PubMed1995

Electrophysiological correlates of psychopathology in individuals with mental retardation and epilepsy.

One hundred adults with mental retardation and epilepsy were randomly selected from hospital and community settings for a detailed study of psychopathology (maladaptive behaviour, psychiatric illness and personality disorder). All of them had a recording of interictal EEG within the 12-month study period. Of all the EEG recordings, nine were completely normal, 48 showed excessive slow background wave, and a further 43 showed epileptiform discharges. Of the 43 with epileptiform discharges in the EEG, 12 showed bilateral, diffuse, generalized activities (including 3 Hz abnormality), 18 showed temporal lobe focus (five left-sided, four right-sided and nine bilateral), and the other 13 showed secondary generalization from a temporal lobe focus. A comparison of psychopathology between the groups with a generalized epileptiform activity in the EEG (n = 12) and focal changes (n = 18) did not reveal any significant differences.

Adult↗
PubMed1995

Wild-type human p53 transactivates the human proliferating cell nuclear antigen promoter.

The wild-type p53 protein is a transcriptional activator implicated in the control of cellular growth-related gene expression. Here, using a number of different cell lines and transient-transfection-transcription assays, we demonstrate that at low levels, wild-type p53 transactivates the human proliferating cell nuclear antigen (PCNA) promoter. When expressed at a similar level, the tumor-derived p53 mutants did not transactivate the PCNA promoter. We identified a p53-binding site on the human PCNA promoter with which p53 interacts sequence specifically. When placed on a heterologous synthetic promoter, the binding site functions as a wild-type p53 response element in either orientation. Deletion of the p53-binding site renders the PCNA promoter p53 nonresponsive, showing that wild-type p53 transactivates the PCNA promoter by binding to the site. At a higher concentration, wild-type p53 inhibits the PCNA promoter but p53 mutants activate. Transactivation by p53 mutants does not require the p53-binding site. These observations suggest that moderate elevation of the cellular wild-type p53 level induces PCNA production to help in DNA repair.

3T3 Cells↗
PubMed1995

The pattern of psychiatric admissions to a hospital for people with a learning disability in the Grampian region between 1989 and 1991.

It is known that a substantial proportion of people with a learning disability also have associated emotional problems in the form of psychiatric illness and disturbed behaviour. In the UK various health authorities are developing in-patient facilities for assessment and treatment of this group of people by default rather than by planning. We report the prospective findings of psychiatric admissions to a hospital for learning disabled people in the Grampian region of Scotland over a three year period between 1.1.89 to 31.12.91. Nine beds were deemed necessary for a health district with a general population of 500,000. Average bed occupancy was 66.7%. The most common conditions leading up to an admission was disturbed behaviour followed by affective disorder and psychoses. The majority of the admissions were of adults with a mild to moderate degree of learning disability as opposed to severe and profound learning disability. A hard-core group of patients had many re-admissions. Some acute admissions became long-stays (over one year), although average stay of admissions were between four to six weeks.

Adult↗
PubMed1994

Cell-type-specific induction of the UL9 gene of HSV-1 by cell signaling pathway.

The origin-binding protein, encoded by the UL9 gene of herpes simplex virus-1 (HSV-1), has the properties of an initiator of DNA replication. In this communication, we report that the UL9 promoter contains a cAMP-response element (CRE). Transient expression analyses show that dibutyryl cyclic AMP, known to elevate intracellular cAMP level, can induce the UL9 promoter in a rat pheochromocytoma cell line (PC12) but not in a non-neuronal human cell line (HeLa). Interestingly, a transcription factor that increases expression of a neuropeptide gene by interacting with CRE can also activate the UL9 promoter independent of cell type. Thus, our data suggest that extracellular stimuli, capable of interacting with the signaling pathway in neuronal cells, can activate UL9 gene expression, and different proteins may regulate UL9 expression in different cell types.

Animals↗
PubMed1994

Spontaneous differentiation of trophoblast cells along the spongiotrophoblast cell pathway: expression of members of the placental prolactin gene family and modulation by retinoic acid.

The purpose of this study was to examine part of the trophoblast cell multilineage pathway and its modulation by retinoic acid. A method for studying trophoblast cell differentiation along the spongiotrophoblast cell pathway in vitro was established and characterized. Cells were isolated from junctional zones of Day 13 rat chorioallantoic placentas via mechanical dissection, enzymatic digestion, and enrichment through a Percoll cushion. The cells were cultured up to 8 days and analyzed for their purity, morphology, and ability to express members of the placental prolactin (PRL) family. Cell preparations contained minimal mesenchymal contamination as estimated by immunocytochemical analysis for vimentin. The cells expressed PRL-like protein-A (PLP-A), PLP-B, PLP-C, and placental lactogen-I variant (PL-Iv) indicative of their differentiated spongiotrophoblast cell phenotype. Expression of members of the PRL family increased markedly during culture. Temporally the increase in PLP-A expression preceded the increased expression of PLP-B (0.9 kb), PLP-C, and PL-Iv. These in vitro observations paralleled the behavior of spongiotrophoblast cells developing in situ. Some differences were evident, including the immediate activation of PLP-B (1.2 kb) following enzymatic isolation of the cells. These cells were also susceptible to experimental manipulation. Exposure to retinoic acid influenced the morphology of the cells and the profile of members of the placental PRL family expressed by in vitro differentiated cells. In summary, a culture system has been devised to examine the control of spongiotrophoblast cell differentiation and the regulation of expression of members of the placental PRL gene family. Spongiotrophoblast cells spontaneously differentiate in vitro through discrete developmental phases that are susceptible to modulation by retinoic acid.

Animals↗
PubMed1994

Analysis of the DNA-binding domain of the HSV-1 origin-binding protein.

In order to understand DNA-protein interactions at the origin of DNA replication in herpes simplex virus type 1 (HSV-1), we have undertaken an analysis of the DNA-binding domain of the origin-binding protein (OBP) and its mechanism of binding to the Oris sequence of HSV-1. Mutant DNA-binding domains were constructed, expressed in vitro, and used to test for binding by gel shift analysis. A C-terminal deletion mutant was functional in binding, thereby redefining the C-terminal boundary of the DNA-binding domain at amino acid 822. Fifteen insertion mutants were also constructed across the DNA-binding domain. Several of these mutants were unable to bind DNA. Interestingly, 4 mutants that destroy DNA binding fall within a region that has a particularly high degree of sequence similarity to the varicella zoster virus gene 51 product. A second objective was to define how the DNA-binding domain interacts with the origin. Results of gel shift analysis using contranslated proteins of different sizes suggest that the DNA-binding domain can interact with a single binding site as a monomer. Binding to the wild-type Oris template indicated that the binding domains can interact with both binding sites I and II independent of any cooperative effect mediated by the amino-termini. This suggests that the basic unit of recognition involved in OBP/Oris interactions may contain a single DNA-binding domain of OBP in association with a single binding site.

Amino Acid Sequence↗
PubMed1994

Novel hydroxyapatite-based dental composites.

Newly designed composite resins for dental applications have been studied. The matrix phases were based on 2,2 bis-4(2-hydroxy-3-methacryloyloxypropoxy)phenyl propane and a urethane dimethacrylate. Tetrahydrofurfuryl methacrylate was added as a diluent to both dimethacrylates in a proportion of 30 wt%. Heat-cured composite resins were obtained with filler weight fractions of 60% and 67%. After surface treating hydroxyapatite powder with a silane coupling agent, filler contents of 60%, 67% and 80% were employed. These materials were then evaluated for Young's modulus, flexural strength, diametral tensile strength and Vickers hardness. With the exception of Young's modulus, all mechanical properties of the tested materials were significantly improved when a silanized hydroxyapatite filler had been used.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1994

Polydipsia amongst adults with a learning disability in an institution.

A hospital-based adult learning disabled population (n = 371) was screened for polydipsia with the help of a purpose-designed questionnaire. Polydipsia was defined as excessive drinking of more than 3 l of non-alcoholic fluid over a 24-h period. Altogether, 23 (6.2%) subjects were found to have polydipsia. The polydipsic group was compared with the whole hospital population on variables such as age and IQ distribution. A matched group of 23 individuals without a history of polydipsia was drawn from the same hospital population. The polydipsic and the matched group were compared using various biochemical and psychological measures. Thirty-five per cent of polydipsic patients, compared to 13% of the matched group, showed evidence of compensated hyponatraemia. This difference was not significant. There was no significant difference between the polydipsic and the matched group in the frequency of psychiatric illness, behavioural problems or autism. There also was no significant difference in the IQ levels of the polydipsic patients and the total hospital population. Polydipsia in this population is largely seen as part of an abnormal behavioural repertoire without any evidence of possible organic cause, except unidentified diabetes mellitus. Klein Levin syndrome and pica were represented in the polydipsic group, but not amongst the matched group.

Adult↗
PubMed1994

Activation of the human immunodeficiency virus type 1 long terminal repeat by transforming mutants of human p53.

We have studied the effects of human wild-type and mutant p53s on the long terminal repeat (LTR) promoter of human immunodeficiency virus type 1 (HIV). HeLa cells were cotransfected with a wild-type or mutant p53 expression plasmid and a plasmid containing a chloramphenicol acetyltransferase reporter gene under HIV LTR promoter control. As expected, expression of wild-type p53 inhibited promoter function. Expression of a p53 mutated at any one of the four amino acid positions 175, 248, 273, and 281 correlated with a significant increase of the HIV promoter activity. The HIV LTR was also significantly activated in Saos-2 cells that do not express endogenous p53. This finding suggests a gain-of-transactivation function by mutation of the p53 gene. Cotransfection of wild-type and mutant p53-281G expression plasmids indicated that either the wild type or the mutant was dominant in inhibiting or enhancing promoter activity, respectively, when transfected in excess of the other. Transfection experiments showed transactivation even when the Sp1, NF-kappa B, and TATA sites in the LTR were individually mutated. Synthetic minimal promoter constructs containing two Sp1 sites or two NF-kappa B sites or an ATF site are also significantly activated by the mutant p53-281G. Thus, the mutant protein may activate transcription through interaction with either a general transcription factor or a common factor that bridges the basal transcription machinery and the transcription factors Sp1, NF-kappa B, and ATF.

Activating Transcription Factors↗
PubMed1994

Cloning and expression of an equine herpesvirus 1 origin-binding protein.

Equine herpesvirus 1 (EHV-1) is an important pathogen of horses and is closely related to several important human pathogens, herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) and varicella-zoster virus. The EHV-1 genome contains open reading frames similar in sequence to the HSV-1 replication genes. PCR was used to clone EHV-1 gene 53, which is similar in sequence to the HSV-1 UL9 gene. The gene 53 product has regions of striking similarity to the HSV-1 UL9 and VZV gene 51 products. In vitro transcription and translation of this gene generated a protein of 87 kDa as measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Further characterization of this protein was accomplished through the use of gel shift analysis. The in vitro-synthesized protein bound sequence specifically to EHV-1 OriS as well as HSV-1 OriS. A site was used in gel shift analysis to show that the EHV-1 origin-binding protein bound to the same consensus site as the HSV-1 origin-binding protein, 5'-CGTTCGCACTT-3'. Using a nuclear extract of EHV-1-infected RK13 cells, we have identified an activity that interacts similarly with this consensus site. In gel shift assays, the retarded band arising from the nuclear extract migrated similarly to the retarded band arising from in vitro-translated EHV-1 gene 53. An N-terminal deletion of EHV-1 gene 53 was also created, expressed in vitro, and used in gel shift assays to localize the DNA-binding domain. Results of these experiments indicated that amino acids 1 to 499 were dispensable for binding and that the C-terminal fragment (amino acids 500 to 888) recognized the same consensus site as did the wild-type protein. Thus, the product of EHV-1 gene 53 is an origin-binding protein with a high degree of similarity to the HSV-1 and varicella-zoster virus origin-binding proteins and possibly serves as the initiator of DNA replication in EHV-1.

Animals↗
PubMed1994

The prevalence of autistic disorder among children with a learning disability.

BACKGROUND: It has been suggested recently that the prevalence of autistic disorder may be rising. No prevalence study specifically among learning disabled children exists and so this study was prompted. METHOD: 767 children with a learning disability who attended 16 different special schools in the Grampian region of north-east Scotland were studied for a diagnosis of autistic disorder according to the DSM-III-R criteria. The study was conducted in three stages. In the first screening stage, a questionnaire was completed for each child by their teachers. In the second stage, teachers completed another questionnaire based on DSM-III-R criteria for autistic disorder. A final diagnosis was made on the basis of examination and information gathered from the questionnaires. RESULTS: Questionnaires were completed for 634 (82.7%) children. 14.3% of children with a learning disability fulfilled the diagnostic criteria for autistic disorder. There was a male:female ratio of 3:1. This gave a 9 per 10,000 minimum prevalence of autistic disorder among all school-age children in the Grampian region. There was a higher prevalence of autistic disorder in the cities compared with rural areas. The prevalence did not change with age but increased with decreasing IQ. CONCLUSION: The results of the study support the view that there may be an increasing prevalence of reported cases of autistic disorder.

Adolescent↗