RESUMEN
Drosophila circadian oscillators comprise interlocked period (per)/timeless (tim) and Clock (Clk) transcriptional/translational feedback loops. Within these feedback loops, CLOCK (CLK) and CYCLE (CYC) bind E-box elements to activate per and tim transcription, and we now show that at the same time CLK-CYC repress Clk by activating the transcriptional repressor vrille (vri), thus accounting for the opposite cycling phases of these transcripts and identifying vri as the negative component of the Clk-feedback-loop. The core oscillator mechanism is assumed to be the same for oscillators in different tissues. However, we have shown that CRYPTOCHROME (CRY) has a light-independent function in the oscillator that controls olfaction rhythms, suggesting that CRY may function within the oscillator mechanism itself as it does in mammals. These olfaction rhythms require the function of 'peripheral' oscillators which are distinct from the 'central' lateral neuron (LN) oscillators that mediate locomotor activity rhythms. Preliminary results show that antennal oscillator cells are sufficient and LNs are not necessary for olfaction rhythms, indicating that unlike the situation in mammals, the central oscillator has little impact on the olfaction rhythm oscillator under these conditions.
Asunto(s)
Ritmo Circadiano/fisiología , Drosophila/fisiología , Animales , Proteínas CLOCK , Ritmo Circadiano/genética , Criptocromos , Drosophila/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/fisiología , Proteínas del Ojo/genética , Proteínas del Ojo/fisiología , Retroalimentación , Genes de Insecto , Modelos Biológicos , Proteínas Nucleares/genética , Proteínas Nucleares/fisiología , Proteínas Circadianas Period , Células Fotorreceptoras de Invertebrados/fisiología , ARN/genética , ARN/metabolismo , Receptores Acoplados a Proteínas G , Factores de Transcripción/genética , Factores de Transcripción/fisiologíaRESUMEN
In the Drosophila circadian clock, daily cycles in the RNA levels of dclock (dClk) are antiphase to those of period (per). We altered the timing/levels of dClk expression by generating transgenic flies whereby per circadian regulatory sequences were used to drive rhythmic transcription of dClk. The results indicate that posttranscriptional mechanisms make substantial contributions to the temporal changes in the abundance of the dCLK protein. Circadian regulation is largely unaffected in the transgenic per-dClk flies despite higher mean levels of dCLK. However, in per-dClk flies the duration of morning activity is lengthened in light-dark cycles and light pulses evoke longer lasting bouts of activity. Our findings suggest that, in addition to a role in generating circadian rhythms, dCLK modulates the direct effects of light on locomotion.
Asunto(s)
Proteínas de Drosophila/genética , Luz , Actividad Motora/fisiología , Procesamiento Postranscripcional del ARN/fisiología , Factores de Transcripción/genética , Animales , Animales Modificados Genéticamente/genética , Animales Modificados Genéticamente/metabolismo , Proteínas CLOCK , Ritmo Circadiano/fisiología , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/fisiología , Drosophila melanogaster/genética , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Masculino , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas Circadianas Period , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Transcripción/metabolismo , Factores de Transcripción/fisiologíaRESUMEN
Cellular aging is accompanied by increased cellular permeability to zinc(II). The intrinsic zinc content of human diploid fibroblast cells increases with cell age, so that it quadruples from early to late passage, on a Zn(II) per cell or per cell volume basis, but it remains constant on a Zn(II) per protein basis. When the cells are challenged with toxic concentrations (0.2 mM) of Zn(II), both the rate of zinc incorporation into the cells and the amount of zinc incorporated at equilibrium increases considerably with age (unless measured as zinc per protein). In terms of growth inhibition, Zn(II) is more toxic to the cell than Cu(II), Mn(II), or Mg(II).