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1.
Biochim Biophys Acta ; 1219(2): 380-8, 1994 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-7522572

RESUMO

It has been proposed that Asp-443, Glu-478, and Asp-498 are important in RNase H mediated catalysis by human immunodeficiency virus-1 reverse transcriptase (Davies J.F., Hostomska, Z. Hostomsky, Z., Jordan, S.R. and Matthews, D.A. (1991) Science 251, 88-95; Mizrahi, V., Usdin, M.T., Harington, A. and Dudding, L.R. (1990) Nucleic Acids Res. 18, 5359-5363). Single point mutations at either position 443 (Mizrahi, V., Usdin, M.T., Harington, A. and Dudding, L.R. (1990) Nucleic Acids Res. 18, 5359-5363) or 478 (Schatz, O., Cromme, F.V., Grüninger-Leitch, F. and Le Grice, S.F.J. (1989) FEBS Lett. 257, 311-314) severely inhibit RNase H activity but have only small effects on polymerase activity. We show here that a single mutation at position 498 of Asp to Asn (mutant D498N) results in a stable enzyme with a 20-fold reduction in the ratio of RNase H to polymerase activity. The mutant and wild type enzymes were equally processive, paused in the same locations, and extended primers at the same rate during DNA synthesis on a heteropolymeric RNA template. The rate of elongation on the homopolymeric template poly(rA) was also the same. The results indicate that the mutation does not affect normally measured catalytic parameters of the polymerase function of the enzyme. D498N catalyzed strand transfer synthesis on homopolymeric, but not heteropolymeric templates, indicating that RNase H activity is not required for the former activity, but is for the latter.


Assuntos
HIV-1/enzimologia , DNA Polimerase Dirigida por RNA/química , Ribonuclease H/metabolismo , Asparagina/química , Ácido Aspártico/química , Sequência de Bases , DNA Polimerase Dirigida por DNA/química , Transcriptase Reversa do HIV , Dados de Sequência Molecular , DNA Polimerase Dirigida por RNA/metabolismo , Especificidade por Substrato , Moldes Genéticos
2.
Science ; 241(4874): 1820-3, 1988 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-3051378

RESUMO

Interleukin-3 (IL-3) is a member of a family of growth factors, each of which supports the proliferation and development of hematopoietic precursors in culture. Although the biologic effects of the different hematopoietic growth factors have been well documented in different culture systems, it has only recently become possible to study the activities of these molecules in vivo. In comparison with the later acting hematopoietic growth factors granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor, IL-3 elicited a delayed and relatively modest leukocytosis when continuously infused intravenously in primates. The IL-3 infusion, however, greatly potentiated the responsiveness of the animal to subsequent administration of a low dose of GM-CSF. These results suggest that IL-3 expands an early cell population in vivo that subsequently requires the action of a later acting factor such as GM-CSF to complete its development. Optimal stimulation of hematopoiesis may be achieved with combinations of hematopoietic growth factors.


Assuntos
Fatores Estimuladores de Colônias/farmacologia , Substâncias de Crescimento/farmacologia , Hematopoese/efeitos dos fármacos , Interleucina-3/farmacologia , Animais , Sinergismo Farmacológico , Fator Estimulador de Colônias de Granulócitos e Macrófagos , Contagem de Leucócitos , Macaca fascicularis , Fatores de Tempo
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