PubMed Health⌕ Search

Biomedical subjects

J D Gupta

Publications and source records attributed to J D Gupta.

At least 19 recordsLinked to original sources
PubMed2001

Position and sequence requirements for poly(A) length regulation by the poly(A) limiting element.

The poly(A)-limiting element (PLE) is a cis-acting sequence that acts to limit poly(A) tail length on pre-mRNA to <20 nt. Functional PLEs are present in a number of genes, underscoring the generality of this control mechanism. The current study sought to define further the position requirements for poly(A) length regulation and the core sequence that comprises a PLE. Increasing the spacing between the PLE and the upstream 3' splice site or between the PLE and the downstream AAUAAA had no effect on poly(A) length control. However, moving the PLE from the terminal exon to either an upstream exon or intron eliminated poly(A) length control. Poly(A) length control was further evaluated using a battery of constructs in which the PLE was maintained in the terminal exon, but where upstream introns were either deleted, modified, or replaced with a polypyrimidine tract. Poly(A) length control was retained in all cases, indicating that the key feature is the presence of the PLE in the terminal exon. A battery of mutations demonstrated the importance of the 5' pyrimidine-rich portion of the element. Finally, UV crosslinking experiments identified an approximately 62-kDa protein in Hela nuclear extract that binds to a wild-type 23-nt PLE RNA oligonucleotides but not to a mutated nonfunctional form of the element.

Base Sequence↗
PubMed1998

Polynucleotide phosphorylase is a component of a novel plant poly(A) polymerase.

We have isolated cDNA clones encoding a novel RNA-binding protein that is a component of a multisubunit poly(A) polymerase from pea seedlings. The encoded protein bears a significant resemblance to polynucleotide phosphorylases (PNPases) from bacteria and chloroplasts. More significantly, this RNA-binding protein is able to degrade RNAs with the resultant production of nucleotide diphosphates, and it can add extended polyadenylate tracts to RNAs using ADP as a donor for adenylate moieties. These activities are characteristic of PNPase. Antibodies raised against the cloned protein simultaneously immunoprecipitate both poly(A) polymerase and PNPase activity. We conclude from these studies that PNPase is the RNA-binding cofactor for this poly(A) polymerase and is an integral player in the reaction catalyzed by this enzyme. The identification of this RNA-binding protein as PNPase, which is a chloroplast-localized enzyme known to be involved in mRNA 3'-end determination and turnover (Hayes, R., Kudla, J., Schuster, G., Gabay, L., Maliga, P., and Gruissem, W. (1996) EMBO J. 15, 1132-1141), raises interesting questions regarding the subcellular location of the poly(A) polymerase under study. We have reexamined this issue, and we find that this enzyme can be detected in chloroplast extracts. The involvement of PNPase in polyadenylation in vitro provides a biochemical rationale for the link between chloroplast RNA polyadenylation and RNA turnover which has been noted by others (Lisitsky, I., Klaff, P., and Schuster, G. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 13398-13403).

Amino Acid Sequence↗
PubMed1996

A plant poly(A) polymerase requires a novel RNA-binding protein for activity.

We have purified a novel factor (PAP-III) that is a component of a multisubunit poly(A) polymerase from pea seedlings. This factor consists of one or more polypeptides with molecular masses of about 105 kDa and of a population of associated RNAs that can serve as substrates for polyadenylation. When these RNAs are separated from the 105-kDa polypeptides, polyadenylation becomes dependent upon exogenously added RNA. This RNA-dependent activity does not require the presence of a polyadenylation signal in the substrate, indicating that the activity under study is a nonspecific polyadenylation activity. One or more of the 105-kDa polypeptides could be cross-linked to the products of polyadenylation labeled with [alpha-32P]ATP and to exogenously added labeled RNAs. Cross-linking of the 105-kDa polypeptides to the products of polyadenylation was not affected by the presence of exogenously added competitors, whereas cross-linking to exogenous RNAs was diminished by excesses of RNA homopolymers. Exogenous RNAs could be polyadenylated by the combination of PAP-I + PAP-III, and this activity was diminished if the binding of the exogenous RNAs to PAP-III was prevented. We conclude from these studies that PAP-III is an RNA binding protein, that polyadenylation by the poly(A) polymerase occurs while the substrate RNAs are associated with this protein, and that the pea poly(A) polymerase can only polyadenylate those RNAs that are associated with PAP-III.

Cross-Linking Reagents↗
PubMed1994

Influence of dietary restriction and soyabean supplementation on the growth of a murine lymphoma and host immune function.

A comparative study was made to reveal the influence of caloric restriction with or without soyabean in the diet on the growth of a murine lymphoma, host survival, serum profile of vitamin A and E and immune status of the host. Caloric restriction delayed and inhibited tumour growth and improved host survival; inclusion of soyabean during restriction enhanced this effect. Dietary restriction both in the absence and presence of soyabean improved the proliferative response of peripheral blood lymphocytes. This was accompanied by increased cytolytic activity of peritoneal macrophages and elevation in serum immunoglobulins (IgG and IgM). Levels of vitamins A and E, which is found to be low in tumour bearing animals, decreased further when maintained in the restricted diet without soyabean, but was raised to normal levels following addition of soyabean in the diet. These observations imply that tumour growth is arrested possibly by insufficient nutrition available due to dietary restriction, for actively proliferating tumour cells and by improvement in host immune mechanism in the presence of soyabean in the diet.

Animals↗
PubMed1992

Experimental evaluation of preventive and therapeutic potentials of lysozyme.

Therapeutic efficacy and preventive role of egg white lysozyme was evaluated in three types of murine ascitic tumours, namely sarcoma 180, Ehrlich's carcinoma, and Dalton's lymphoma. Lysozyme treatment produced regression of tumour growth and improved the life expectancy of the host. Growth of tumour cells treated in vitro with lysozyme prior to transplantation was also affected. In addition, lysozyme was found to have a preventive effect when administered to normal mice. The antitumour activity, therapeutic and preventive, of lysozyme seems to be due to its action on the tumour cell surface as well as on the host-mediated immune response.

Animals↗
PubMed1988

Chronic arsenic toxicity from drinking tubewell water in rural West Bengal.

Hepatic damage caused by chronic exposure to arsenic has been frequently described. Here we report on 13 patients from West Bengal, India, who consumed large amounts of arsenic in drinking water. An epidemiological investigation of the study area showed evidence of chronic arsenical dermatosis and hepatomegaly in 62 (92.5%) of 67 members of families who drank contaminated water (arsenic level, 0.2-2 mg/l). In contrast, only six (6.25%) of 96 persons from the same area who drank safe water (arsenic level, <0.05 mg/l) had non-specific hepatomegaly, while none had skin lesions. Hepatomegaly occurred in all the 13 patients who were studied in detail, although five had splenomegaly. Biopsy of samples of liver from these patients revealed various degrees of fibrosis and expansion of the portal zone that resembled non-cirrhotic portal fibrosis (NCPF).

Adolescent↗
PubMed1980

Levels of glycolytic enzymes in the red blood cells of Australian Aborigines.

Blood samples wer collected from three populations of full-blood Aborigines, and twelve different enzymes were assayed in red blood cells. These results were compared with those of Caucasian controls. In the majority of enzymes studied significant differences were observed between the Aboriginal populations and also between individual Aboriginal populations and the Caucasian controls.

Alcohol Oxidoreductases↗
PubMed1979

Effect of other drugs and chemicals on the degradation of aspirin in vitro: possible extrapolation to in vivo metabolism of aspirin.

To assess the possible influence of other drugs and chemicals on the metabolic degradation of aspirin in man, their effect on the serum aspirin esterase activity was determined in vitro. The activation or inhibition of the enzyme as observed with these compounds suggest the possibility that simultaneous ingestion of these drugs with aspirin may influence the pharmacology and toxicity of the analgesic.

Anticoagulants↗
PubMed1977

Serum aspirin esterase activity in women with habitual aspirin intake.

A method for the determination of aspirin esterase activity in serum is described. Sera from 59 pregnant women who were habitual aspirin users were found to have a mean enzyme activity value statistically lower than those of 68 non-pregnant women controls or of 12 pregnant women controls who were either occasional users of the drug or were non-users. The distribution of enzyme activity in the experimental group was also significantly different from that of the control group. It is postulated that the low enzyme activity may further aggravate the injurious effects of high intake of aspirin.

Adult↗
PubMed1975

Galactose metabolism in relation to cataract formation in marsupials.

Erythrocytic galactokinase and/or galactose-1-phosphate uridyl transferase activity were low in many species of marsupials. However, cataract formation was observed only in pouch-young members of these species when reared on cow's milk. The galactose tolerance of young kangaroos was found to be greatly impaired, but improved rapidly and markedly at the stage of which the definitive structure of the ruminant type of stomach as in adults is formed. The combination of high absorption of galactose and low levels of galactokinase and/or transferase thus appears to determine the predisposition of pouch-young marsupials to galactose cataractogenesis.

Adult↗