Ajit K Chakraborty

Learn More
The pattern of human retinoblastoma (RB1) gene protein expression was directly examined in normal and malignant human colorectal tissues and in seven colorectal carcinoma cell lines by immunohistochemistry using the mouse monoclonal antibody (RB-MAb-1) directed against the retinoblastoma protein (RB). This is the first demonstration of RB immunostaining in(More)
Sodium stibogluconate and Ureastibamine, two potent antileishmanial drugs specifically inhibit the relaxation of supercoiled plasmid pBR322 catalyzed by DNA topoisomerase I of Leishmania donovani. Dose dependent inhibition suggests that the drugs interact with the enzyme rather than the DNA. The inhibition reported here concerning a type I DNA topoisomerase(More)
New gene therapy methods are rapidly being developed to permit the expression of tumor suppressor genes, cytotoxins, anticancer antigens, and immunoregulatory proteins in the treatment of cancer. Large-scale testing in humans has been delayed by questions concerning the safety and effectiveness of preferred retroviral vectors and helper cells. These vector(More)
A type 1 DNA topoisomerase has been purified from the nuclei of the kinetoplast hemoflagellate Leishmania donovani using polyethylene glycol fractionation and chromatography on hydroxylapatite, phosphocellulose and phenylsepharose column. The relaxation activity is ATP independent. Mg2+ is an essential cofactor for the reaction with an optimum at 10 mM.(More)
An enzyme from Leishmania donovani that decatenates kinetoplast DNA networks into covalently closed monomeric circles has been isolated and characterized. The enzyme also relaxes supercoiled plasmid pBR322. The decatenation and relaxation reactions both require ATP and Mg2+. In both reactions the formation of topological isomers of unique linking numbers(More)
An enzyme from Leishmania donovani that catenates monomeric pBR322 into huge catenanes has been isolated and characterized. The enzyme also decatenates kinetoplast DNA networks into covalently closed monomeric circles and relaxes supercoiled pBR322. The catenation, decatenation and relaxation reactions do not require ATP. The formation of topological(More)
Retrovirus-derived vectors and packaging cell lines are basic components used for gene transfer in human gene therapy. To eliminate recombinational and transcriptional problems associated with retroviral vectors, synthetic retrotransposon VL30 vectors were devised. During experimentation with these new vectors, extensive cotransmission of endogenous VL30(More)
Novel vectors made from mouse VL30 retrotransposons were tested in cell types that are targets for gene therapy, including normal human cells (skeletal muscle epithelium, bronchial epithelium, mammary epithelium), Epstein-Barr virus-transformed peripheral blood lymphocytes (PBLs), and various tumor cell lines. The long terminal repeat (LTR) transcriptional(More)
The far upstream region of the rat Ha-ras gene has been characterized to determine whether possible repressor sequences may control the low level of Ha-ras gene transcription from its TATA-less, GC-rich strong promoter. The chloramphenicol acetyl transferase (CAT) gene under the control of the 3.8-kb Ha-ras upstream promoter was minimally expressed in HeLa(More)
Chemical investigation of the leaves of Putranjiva roxburghii has resulted in the isolation of two new triterpenoids, putralone, a novel 10alpha-hydroxy-25-nor D:A friedo-olean-9(11)-en-3 one and 3beta-acetoxy-cycloart-24-en-23-one, along with a rare hopanoid, adian-5-en-3beta,29-diol. Other known triterpenoids isolated from this plant are(More)