| dc.description.abstract | The circadian clock is a conserved endogenous time keeping mechanism that controls up to half of the eukaryotic genome at the level of transcript abundance. In addition to clock control of transcript abundance, our lab discovered that the Neurospora crassa clock controls mRNA translation through the rhythmic and inhibitory phosphorylation of eukaryotic translation initiation factor subunit, eIF2α. In wild type N. crassa, phosphorylated eIF2α (P-eIF2α) peaks during the day and troughs at night, resulting in increased mRNA translation at night. N. crassa CPC-3, the homolog of yeast and mammalian GCN2, is the kinase responsible for eIF2α phosphorylation. Several regulators are known to control GCN2 activity in yeast and mammalian cells. My goal is to determine if any of these regulators affect rhythmic activity of CPC-3 and if so, determine how that regulator’s action is clock-controlled. To accomplish this goal, I assayed P-eIF2α levels in strains deleted for the putative regulators. I discovered that P-eIF2α levels remained rhythmic in Δreg1 and ΔeIF4e3 cells. However, in strains deleted for stk-10, P-eIF2α levels were high and arrhythmic. STK-10 is a serine/threonine kinase that may be regulated by the nutrient sensing TOR pathway. Under nutrient rich conditions, TORC1 is active, phosphorylating and activating STK10. Active STK-10 may then phosphorylate and inhibit CPC-3 kinase activity, leading to low levels of P-eIF2α and increased mRNA translation. Thus, the requirement of N. crassa STK-10 for rhythmic P-eIF2α levels suggests a model where at night, TORC1 activates STK-10, and STK10 phosphorylates and inhibits CPC-3 kinase activity, under control of the clock. This would lead to low levels of P-eIF2α, and increased mRNA translation at night. Experiments are currently underway to test this model and to determine if rhythmic activity or abundance of STK-10 is responsible for the rhythmic activity of CPC-3. | en |
