title: Circadian clock regulation of mRNA translation through eukaryotic elongation factor eEF-2.
abstract: The circadian clock has a profound effect on gene regulation, controlling rhythmic transcript accumulation for up to half of expressed genes in eukaryotes. Evidence also exists for clock control of mRNA translation, but the extent and mechanisms for this regulation are not known. In Neurospora crassa, the circadian clock generates daily rhythms in the activation of conserved mitogen-activated protein kinase (MAPK) pathways when cells are grown in constant conditions, including rhythmic activation of the well-characterized p38 osmosensing (OS) MAPK pathway. Rhythmic phosphorylation of the MAPK OS-2 (P-OS-2) leads to temporal control of downstream targets of OS-2. We show that osmotic stress in N. crassa induced the phosphorylation of a eukaryotic elongation factor-2 (eEF-2) kinase, radiation sensitivity complementing kinase-2 (RCK-2), and that RCK-2 is necessary for high-level phosphorylation of eEF-2, a key regulator of translation elongation. The levels of phosphorylated RCK-2 and phosphorylated eEF-2 cycle in abundance in wild-type cells but not in cells deleted for OS-2 or the core clock component FREQUENCY (FRQ). Translation extracts from cells grown in constant conditions show decreased translational activity in the late subjective morning, coincident with the peak in eEF-2 phosphorylation, and rhythmic translation of glutathione S-transferase (GST-3) from constitutive mRNA levels in vivo is dependent on circadian regulation of eEF-2 activity. In contrast, rhythms in phosphorylated eEF-2 levels are not necessary for rhythms in accumulation of the clock protein FRQ, indicating that clock control of eEF-2 activity promotes rhythmic translation of specific mRNAs.
authors: Genetics Program, Texas A&M University, College Station, TX 77843; Center for Biological Clocks Research, Texas A&M University, College Station, TX 77843;
authors: Stephen Z
authors: SZ
authors: Caster
authors: Center for Biological Clocks Research, Texas A&M University, College Station, TX 77843; Department of Biology, Texas A&M University, College Station, TX 77843.
authors: Kathrina
authors: K
authors: Castillo
authors: Department of Biology, Texas A&M University, College Station, TX 77843.
authors: Matthew S
authors: MS
authors: Sachs
authors: Genetics Program, Texas A&M University, College Station, TX 77843; Center for Biological Clocks Research, Texas A&M University, College Station, TX 77843; Department of Biology, Texas A&M University, College Station, TX 77843 dpedersen@bio.tamu.edu.
authors: Deborah
authors: D
authors: Bell-Pedersen
mesh_terms: D057906:Circadian Clocks / Q000235:genetics*; D054736:Elongation Factor 2 Kinase / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D009492:Neurospora crassa / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D009997:Osmotic Pressure; D010441:Peptide Chain Elongation, Translational; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D005982:Glutathione Transferase; C407464:RCK2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D054736:Elongation Factor 2 Kinase; D020928:Mitogen-Activated Protein Kinases; C450461:os-2 protein, Neurospora crassa; D048051:p38 Mitogen-Activated Protein Kinases
keywords: Neurospora crassa; circadian clock; eEF-2; translation; translation elongation