Circadian regulation of oxidative stress-induced Stress Granules

PUSTERLA JM; LESCANO JI; ACOSTA-RODRÍGUEZ VA; GUIDO ME; GARBARINO PICO E

Congreso; SRBR 2014; 2014

Society for Research on Biological Rhythms (SRBR)

It is believed that the exposition to high levels of UV-radiation during the daytime was one of the strongest selective forces that led to circadian rhythms emergence. Accordingly, the stress response is circadianly modulated in numerous model systems. When are exposed to stress, many cell types form microscopically visible foci called stress granules (SG). SG are mainly formed by stalled translational initiation complexes. Since a number of SG components display circadian rhythms, we hypothesized that SG formation may be circadian regulated. To investigate that, we administrated arsenite to synchronized NIH3T3 cell cultures to generate oxidative stress and induce the formation of SG. We found temporal changes in number, signal intensity and size of arsenite-induced SG detected with an anti-eIF3 antibody by ICC. Since total eIF3 protein levels remained constant across the time, the temporal differences observed suggest a redistribution of the protein. Furthermore, we did not find any change along time in the phosphorylation of eIF2α, an event involved in SG nucleation. We next analyzed the mRNA levels of several RNA-binding proteins that are component of SG and could be involved in the temporal changes observed. Interesting, Tia1, Brf1, hnRNPQ, and Lark transcripts presented temporal changes in their levels. Indeed, we observed important circadian changes in the expression of TIA-1, a protein capable of inducing SG nucleation. We also detected that LARK protein levels (also known as RBM4) were highly induced by oxidative stress and the magnitude of these induction was time-dependent. Our results show that SG formation exhibits circadian rhythms and that this phenomenon may be involved in the circadian regulation of stress response.