Wynik wyszukiwania w bazie Polska Bibliografia Lekarska GBL

Zapytanie: MAJUMDER
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Tytuł oryginału: Carboxy terminal domain of the largest subunit of RNA polymerase II of Leishmania donovani has an unusually low number of phophorylation sites.
Autorzy: Dasgupta Arindam, Sharma Shalini, Das Aditi, Sarkar Dwijen, Majumder Hemanta K.
Źródło: Med. Sci. Monitor 2002: 8 (5) s.CR341-CR350, il., tab., bibliogr. 36 poz.
Sygnatura GBL: 313,278

Hasła klasyfikacyjne GBL:
  • genetyka
  • mikrobiologia

    Typ dokumentu:
  • praca doświadczalna
  • tytuł obcojęzyczny

    Wskaźnik treści:
  • zwierzęta

    Streszczenie angielskie: The C-terminal domain (CTD) of the largest subunit of RNA polymerase II in higher eukaryotes has an altered form in Leishmania donovani. To determine whether this is a general feature of the kinetoplastida and to investigate the role of this domain in parasitic RNA pol II transcription, we isolated the gene encoding RNA pol II LS (rpol IILS) and analyzed its C-terminal domain. The discreteness observed may be due to a functional constraint delineating parasite from host. The gene for L. donovani rpol IILS was picked up and sequenced. The CTD of L. donovani rpolIILS was purified as a His-tagged recombinant protein and phosphorylated with a crude kinase extract from L. donovani. An immunoblot analysis of the phosphorylated CTD and photo-crosslinked L. donovani nuclear extracts was done using anti-CTD antibody. The L. donovani rpol IILS is encoded by a single-copy gene. Its transcript is matured posttranscriptionally, with the mini-exon trans-spliced 397 bases upstream of the initiation site. The uniqueness of Leishmania rpol IILS CTD according to prediction analysis was corroborated with in vitro phosphorylation of the recombinant protein. Photoaffinity labelling of L. donovani nuclear run-on transcripts and immunoblot analysis using anti-CTD antibody could identify the active form of RNA polymerase II enzyme in this parasite. The L. donovani rpol IILS possesses a unique C-terminal extension lacking the characteristic repeats but containing serine residues as a potential phosphorylation site. Anti-CTD antiabody could recognize a single molecular species for the RNA pol II enzyme in L. donovani.

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    Tytuł oryginału: Betulinic acid, a potent inhibitor of eukaryotic topoisomerase I: identification of the inhibitory step, the major functional group responsible and development of more potent derivatives.
    Autorzy: Chowdhury Arnab Roy, Mandal Suparna, Mittra Bidyottam, Sharma Shalini, Mukhopadhyay Sibabrata, Majumder Hemanta K.
    Źródło: Med. Sci. Monitor 2002: 8 (7) s.BR254-BR260, il., tab., bibliogr. 29 poz.
    Sygnatura GBL: 313,278

    Hasła klasyfikacyjne GBL:
  • onkologia
  • genetyka
  • farmacja

    Typ dokumentu:
  • praca doświadczalna
  • tytuł obcojęzyczny

    Wskaźnik treści:
  • zwierzęta
  • myszy
  • in vitro

    Streszczenie angielskie: Background: Betulinic acid, a naturally abundant, plant derived, pentacyclic triterpenoid possesses anti-HIV, anti-malarial and anti-inflammatory properties and has recently emerged as a potent anti-tumor compound. This study explores the mode of action of betulinic acid on eukaryotic topoisomerase I and identifies the major functional group responsible along with more potent derivatives. Material/Methods: Topoisomerase I relaxation activity was electrophoretically measured by the decreased mobility of the relaxed monomers followed by ethidium bromide staining. DNA cleavage was studied by electrophoretic separation of the nicked monomers from the relaxed and supercoiled monomers in presence of ethidium bromide. In-vivo DNA cleavage was studied in blasted mouse splenocytes by the SDS-K+ trapping of 3H-DNA-topoisomerase I-camptothecin ternary complex. Results: Betulinic acid exerts its inhibitory effect by preventing topoisomerase I-DNA interaction as a result of which the 'cleavable complex' is not formed. In consequence, it also acts as an antagonist to camptothecin-mediated cleavage. A series of analogues modified at C-3, C-17 and C-20 positions of betulinic acid were subsequently assayed for inhibition of topoisomerase I catalytic activity. Replacemnt of the 17-carboxylic group reduces the inhibitory effect and decarboxylation leads to the complete loss of inhibitory effect. Conclusion: This study is the first detail report of betulinic acid as a very potent inhibitior of eukaryotic topoisomerase I and highlights the necessity of the carboxylic functional group. Dihydro betulinic acid is the most potent (IC50 = 0.5 ćM) pentacyclic triterpenoid to inhibit eukaryotic topoisomerase I till date and can be exploited as a strong candidate for anti-tumor drug designing.

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