Project description:Dietary restriction extends lifespan and delays the age-related physiological decline in many species. Intermittent fasting (IF) is one of the most effective dietary restriction regimens that extends lifespan in C. elegans and mammals1,2. In C. elegans, the FOXO transcription factor DAF-16 is implicated in fasting-induced gene expression changes and the longevity response to IF3; however, the mechanisms that sense and transduce fasting-stress stimuli have remained largely unknown. Here we show that a KGB-1/AP1 (activator protein 1) module is a key signalling pathway that mediates fasting-induced transcriptional changes and IF-induced longevity. Our promoter analysis coupled to genome-wide microarray results has shown that the AP-1-binding site, together with the FOXO-binding site, is highly over-represented in the promoter regions of fasting-induced genes. We find that JUN-1 (C. elegans c-Jun) and FOS-1 (C. elegans c-Fos), which constitute the AP-1 transcription factor complex, are required for IF-induced longevity. We also find that KGB-1 acts as a direct activator of JUN-1 and FOS-1, is activated in response to fasting, and, among the three C. elegans JNKs, is specifically required for IF-induced longevity. Our results demonstrate that most fasting-induced upregulated genes, including almost all of the DAF-16-dependent genes, require KGB-1 and JUN-1 function for their induction, and that the loss of kgb-1 suppresses the fasting-induced upregulation of DAF-16 target genes without affecting fasting-induced DAF-16 nuclear translocation. These findings identify the evolutionarily conserved JNK/AP-1 module as a key mediator of fasting-stress responses, and suggest a model in which two fasting-induced signalling pathways leading to DAF-16 nuclear translocation and KGB-1/AP-1 activation, respectively, integrate in the nucleus to coordinately mediate fasting-induced transcriptional changes and IF-induced longevity. To delineate the whole picture of transcriptional changes in response to fasting, we performed genome-wide gene expression analyses during 2 days (48 h) fasting. Two and three independent experiments were performed in the time course and mutants, respectively.

Project description:Dietary restriction extends lifespan and delays the age-related physiological decline in many species. Intermittent fasting (IF) is one of the most effective dietary restriction regimens that extends lifespan in C. elegans and mammals1,2. In C. elegans, the FOXO transcription factor DAF-16 is implicated in fasting-induced gene expression changes and the longevity response to IF3; however, the mechanisms that sense and transduce fasting-stress stimuli have remained largely unknown. Here we show that a KGB-1/AP1 (activator protein 1) module is a key signalling pathway that mediates fasting-induced transcriptional changes and IF-induced longevity. Our promoter analysis coupled to genome-wide microarray results has shown that the AP-1-binding site, together with the FOXO-binding site, is highly over-represented in the promoter regions of fasting-induced genes. We find that JUN-1 (C. elegans c-Jun) and FOS-1 (C. elegans c-Fos), which constitute the AP-1 transcription factor complex, are required for IF-induced longevity. We also find that KGB-1 acts as a direct activator of JUN-1 and FOS-1, is activated in response to fasting, and, among the three C. elegans JNKs, is specifically required for IF-induced longevity. Our results demonstrate that most fasting-induced upregulated genes, including almost all of the DAF-16-dependent genes, require KGB-1 and JUN-1 function for their induction, and that the loss of kgb-1 suppresses the fasting-induced upregulation of DAF-16 target genes without affecting fasting-induced DAF-16 nuclear translocation. These findings identify the evolutionarily conserved JNK/AP-1 module as a key mediator of fasting-stress responses, and suggest a model in which two fasting-induced signalling pathways leading to DAF-16 nuclear translocation and KGB-1/AP-1 activation, respectively, integrate in the nucleus to coordinately mediate fasting-induced transcriptional changes and IF-induced longevity. To delineate the whole picture of transcriptional changes in response to fasting, we performed genome-wide gene expression analyses during 2 days (48 h) fasting.

Project description:Identifying the physiological functions of microRNAs (miRNAs) is often challenging because miRNAs commonly impact gene expression under specific physiological conditions through complex miRNA::mRNA interaction networks and in coordination with other means of gene regulation, such as transcriptional regulation and protein degradation. Such complexity creates difficulties in dissecting miRNA functions through traditional genetic methods using individual miRNA mutations. To investigate the physiological functions of miRNAs in neurons, we combined a genetic M-bM-^@M-^\enhancerM-bM-^@M-^] approach complemented by biochemical analysis of neuronal miRNA-induced silencing complexes (miRISCs) in C. elegans. Total miRNA function can be compromised by mutating one of the two GW182 proteins (AIN-1), an important component of miRISC. We found that combining an ain-1 mutation with a mutation in unc-3, a neuronal transcription factor, resulted in an inappropriate entrance into the stress-induced, alternative larval stage known as dauer, indicating a role of miRNAs in preventing aberrant dauer formation. Analysis of this genetic interaction suggests that neuronal miRNAs perform such a role partly by regulating endogenous cyclic guanosine monophosphate (cGMP) signaling, potentially influencing two other dauer-regulating pathways. Through tissue-specific immunoprecipitations of miRISC, we identified miRNAs and their likely target mRNAs within neuronal tissue. We verified the biological relevance of several of these miRNAs and found that many miRNAs likely regulate dauer formation through multiple dauer-related targets. Further analysis of target mRNAs suggests potential miRNA involvement in various neuronal processes, but the importance of these miRNA::mRNA interactions remains unclear. Finally, we found that neuronal genes may be more highly regulated by miRNAs than intestinal genes. Overall, our study identifies miRNAs and their targets, and a physiological function of these miRNAs in neurons. It also suggests that compromising other aspects of gene expression, along with miRISC, can be an effective approach to reveal miRNA functions in specific tissues under specific physiological conditions. Each array was used for one biological replicate, where the red channel is used for IP RNA and the green channel is used for Total RNA. IP RNA indicates the transcripts associated with a neuronally expressed, GFP-tagged, miRISC. Five biological replicates were done on asynchronous worms. Please note the two different microarray platforms that were used.

Project description:Identifying the physiological functions of microRNAs (miRNAs) is often challenging because miRNAs commonly impact gene expression under specific physiological conditions through complex miRNA::mRNA interaction networks and in coordination with other means of gene regulation, such as transcriptional regulation and protein degradation. Such complexity creates difficulties in dissecting miRNA functions through traditional genetic methods using individual miRNA mutations. To investigate the physiological functions of miRNAs in neurons, we combined a genetic “enhancer” approach complemented by biochemical analysis of neuronal miRNA-induced silencing complexes (miRISCs) in C. elegans. Total miRNA function can be compromised by mutating one of the two GW182 proteins (AIN-1), an important component of miRISC. We found that combining an ain-1 mutation with a mutation in unc-3, a neuronal transcription factor, resulted in an inappropriate entrance into the stress-induced, alternative larval stage known as dauer, indicating a role of miRNAs in preventing aberrant dauer formation. Analysis of this genetic interaction suggests that neuronal miRNAs perform such a role partly by regulating endogenous cyclic guanosine monophosphate (cGMP) signaling, potentially influencing two other dauer-regulating pathways. Through tissue-specific immunoprecipitations of miRISC, we identified miRNAs and their likely target mRNAs within neuronal tissue. We verified the biological relevance of several of these miRNAs and found that many miRNAs likely regulate dauer formation through multiple dauer-related targets. Further analysis of target mRNAs suggests potential miRNA involvement in various neuronal processes, but the importance of these miRNA::mRNA interactions remains unclear. Finally, we found that neuronal genes may be more highly regulated by miRNAs than intestinal genes. Overall, our study identifies miRNAs and their targets, and a physiological function of these miRNAs in neurons. It also suggests that compromising other aspects of gene expression, along with miRISC, can be an effective approach to reveal miRNA functions in specific tissues under specific physiological conditions.

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Role of the MicroRNA Machinery in Fasting-Induced Gene Expression Changes and Longevity in C. elegans (miRNA)

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