RESUMO
The polytene cells of Drosophila melanogaster larvae are ideally suited for the study of gene information flow during differentiation, in that gene derepression is visualized in the form of chromosomal modifications called puffs. One special group of temperature-sensitive puffs can be experimentally induced within 5 min after transfer of salivary glands from 24-37 degrees C. Glands at 37 degrees C also begin synthesizing several new polypeptides which are of higher molecular weight than the prominent polypeptides being synthesized in glands at 24 degrees C [1]. The present study demonstrates that there is also a shift toward the utilization of heavier or more rapidly sedimenting polyribosomes for protein synthesis in glands transferred from 24-37 degrees C. As a result of such studies it is reasonable to assume that the polyribosome redistribution after a heat shock results from the translation of larger mRNA molecules synthesized by the temperature-sensitive loci. Further studies are suggested to describe the role of heat-induced gene activity in maintaining homeostasis, as well as the manner by which such activity is induced, in cells subjected to dramatic temperature fluctuations.
Assuntos
Polirribossomos/ultraestrutura , Glândulas Salivares/ultraestrutura , Animais , Diferenciação Celular , Cromossomos , Drosophila melanogaster/ultraestrutura , Técnicas In Vitro , Biossíntese de Proteínas , RNA Mensageiro , TemperaturaRESUMO
When Drosophila melanogaster salivary glands are exposed to temperature or dinitrophenol (DNP) treatments, their nucleotide metabolism is altered such that the amount of cellular ATP decreases, whereas the amount of ADP increases. Since both treatments also elicit specific puffing patterns on the salivary gland chromosome, it is suggested that specific loci on the chromosome are activated to form puffs when the efficiency of respiration decreases. The possible relationship between the formation of these puffs and the intramitochondrial metabolism is discussed.
Assuntos
Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Cromossomos/metabolismo , Dinitrofenóis/farmacologia , Glândulas Salivares/metabolismo , Temperatura , Animais , Cromossomos/efeitos dos fármacos , Drosophila melanogaster , Cinética , Consumo de Oxigênio/efeitos dos fármacos , Glândulas Salivares/efeitos dos fármacos , Fatores de TempoAssuntos
Drosophila melanogaster/metabolismo , RNA/metabolismo , Acrilamidas , Animais , Autorradiografia , Biodegradação Ambiental , Mapeamento Cromossômico , Dactinomicina/farmacologia , Drosophila melanogaster/embriologia , Eletroforese , Géis , Temperatura Alta , Larva/metabolismo , Leucina , Peso Molecular , RNA/biossíntese , RNA Ribossômico , Glândulas Salivares/metabolismo , Temperatura , Fatores de Tempo , Trítio , UridinaRESUMO
Fixation with picric acid or formaldehyde retains incorporated [(3)H]acetate which is lost after fixation with ethanol and acetic acid. Unlike [(3)H]uridine, [(3)H]acetate is diffusely incorporated into polytene chromosomes, and not preferentially into existing or newly induced puffs. It is suggested that puff formation does not include an acetylation of histones.
Assuntos
Acetatos/metabolismo , Cromossomos/metabolismo , Histonas/metabolismo , Animais , Autorradiografia , Drosophila , Formaldeído , Ácido Clorídrico , RNA/biossíntese , Glândulas Salivares/citologia , Glândulas Salivares/metabolismo , TrítioRESUMO
Chromosomal puffing, generally believed to represent gene activation in Drosophila, was induced in the presence of radioactively labeled acetate. There is no preferential uptake of these labeled molecules in regions of gene activation. It is concluded that the acetylation of histones does not play a general role in the regulation of RNA synthesis in Drosophila melanogaster.
