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Articles by N Gupta
Total Records ( 5 ) for N Gupta
  L. L Zhu , Y Liu , A. F Cui , D Shao , J. C Liang , X. J Liu , Y Chen , N Gupta , F. D Fang and Y. S. Chang

Peroxisome proliferator-activated receptor- coactivator-1 (PGC-1) is a key regulator of cellular energy metabolism and regulates processes such as adaptive thermogenesis, hepatic gluconeogenesis, fatty acid oxidation, and mitochondrial biogenesis by coactivating numerous nuclear receptors and transcription factors. Here, we demonstrate the presence of the ERR binding site in the regulatory sequence of the glucokinase gene and that PGC-1 coactivates ERR to stimulate the transcription of glucokinase. Simultaneous overexpression of PGC-1 and ERR potently induced the glucokinase gene expression and its enzymatic activity in primary hepatocytes; however, expression of either PGC-1 or ERR alone had no significant effect. Electrophoretic mobility shift and chromatin immunoprecipitation assays revealed the interaction of ERR with the glucokinase promoter. Finally, the knockdown of endogenous ERR with specific siRNA (siERR) or pharmacological inhibition of ERR with XCT790 attenuated insulin-induced glucokinase expression. Taken together, this research identifies glucokinase as a novel target of PGC-1/ERR and underscores the regulatory function of ERR in insulin-dependent enzyme regulation.

  G Fan , Y Fan , N Gupta , I Matsuura , F Liu , X. Z Zhou , K. P Lu and C. Gelinas

The peptidyl-prolyl isomerase Pin1 is frequently up-regulated in human cancers in which Rel/nuclear factor-B (NF-B) is constitutively activated, but its role in these cancers remains to be determined, and evidence is still lacking to show that Pin1 contributes to cell transformation by Rel/NF-B. Rel/NF-B transcriptional and oncogenic activities are modulated by several posttranslational modifications and coregulatory proteins, and previous studies showed that cytokine treatment induces binding of Pin1 to the RelA subunit of NF-B, thereby enhancing RelA nuclear localization and stability. Here we show that Pin1 associates with the Rel subunits of NF-B that are implicated in leukemia/lymphomagenesis and modulates their transcriptional and oncogenic activities. Pin1 markedly enhanced transformation of primary lymphocytes by the human c-Rel protein and also increased cell transformation by the potent viral Rel/NF-B oncoprotein v-Rel, in contrast to a Pin1 mutant in the WW domain involved in interaction with NF-B. Pin1 promoted nuclear accumulation of Rel proteins in the absence of activating stimuli. Importantly, inhibition of Pin1 function with the pharmacologic inhibitor juglone or with Pin1-specific shRNA led to cytoplasmic relocalization of endogenous c-Rel in human lymphoma-derived cell lines, markedly interfered with lymphoma cell proliferation, and suppressed endogenous Rel/NF-B–dependent gene expression. Together, these results show that Pin1 is an important regulator of Rel/NF-B transforming activity and suggest that Pin1 may be a potential therapeutic target in Rel/NF-B–dependent leukemia/lymphomas. [Cancer Res 2009;69(11):4589–97]

  U Kolthur Seetharam , M. M Pradeepa , N Gupta , R Narayanaswamy and M. R. S. Rao

Transition protein 1 (TP1) and TP2 replace histones during midspermiogenesis (stages 12–15) and are finally replaced by protamines. TPs play a predominant role in DNA condensation and chromatin remodeling during mammalian spermiogenesis. TP2 is a zinc metalloprotein with two novel zinc finger modules that condenses DNA in vitro in a GC-preference manner. TP2 also localizes to the nucleolus in transfected HeLa and Cos-7 cells, suggesting a GC-rich preference, even in vivo. We have now studied the localization pattern of TP2 in the rat spermatid nucleus. Colocalization studies using GC-selective DNA-binding dyes chromomycin A3 and 7-amino actinomycin D and an AT-selective dye, 4',6-diamidino-2-phenylindole, indicate that TP2 is preferentially localized to GC-rich sequences. Interestingly, as spermatids mature, TP2 and GC-rich DNA moves toward the nuclear periphery, and in the late stages of spermatid maturation, TP2 is predominantly localized at the nuclear periphery. Another interesting observation is the mutually exclusive localization of GC- and AT-rich DNA in the elongating and elongated spermatids. A combined immunofluorescence experiment with anti-TP2 and anti-TP1 antibodies revealed several foci of overlapping localization, indicating that TP1 and TP2 may have concerted functional roles during chromatin remodeling in mammalian spermiogenesis. (J Histochem Cytochem 57:951–962, 2009)

  N Gupta and E. T. Farinas

Directed evolution is an effective strategy to engineer and optimize protein properties, and microbial cell-surface display is a successful method to screen protein libraries. Protein surface display on Bacillus subtilis spores is demonstrated as a tool for screening protein libraries for the first time. Spore display offers advantages over more commonly utilized microbe cell-surface display systems, which include gram-negative bacteria, phage and yeast. For instance, protein-folding problems associated with the expressed recombinant polypeptide crossing membranes are avoided. Hence, a different region of protein space can be explored that previously was not accessible. In addition, spores tolerate many physical/chemical extremes; hence, the displayed proteins are "preimmobilized" on the inherently inert spore surface. Immobilized proteins have several advantages when used in industrial processes. The protein stability is increased and separations are simplified. Finally, immobilized proteins can be used in a wide array of simple device applications and configurations. The substrate specificity of the enzyme CotA is narrowed. CotA is a laccase and it occurs naturally on the outer coat of B. subtilis spores. A library of CotA genes were expressed in the spore coat, and it was screened for activity toward ABTS [diammonium 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate)] over SGZ (4-hydroxy-3,5-dimethoxy-benzaldehyde azine). A mutant CotA was found to be 120-fold more specific for ABTS. This research demonstrates that B. subtilis spores can be a useful platform for screen protein libraries.

  N Gupta and K. Yuan

We investigate the effect of a stock market liberalization on industry growth in emerging markets. Consistent with the view that liberalization reduces financing constraints, we find that industries that are more externally dependent and face better growth opportunities grew faster following liberalization. However, this growth increase appears to come from an expansion in the size of existing firms rather than through the entry of financially constrained new firms. We show that following liberalization, new firm growth occurs in countries and industries with lower entry barriers. Hence, liberalization has a more uniform growth impact if accompanied by competition-enhancing reforms.

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