Project description:RNA interference (RNAi) pathways are prevalent throughout the eukaryotic kingdom and well known to regulate gene expression on a post-transcriptional level in the cytoplasm. Less is known about possible functions of RNAi in the nucleus. In the fission yeast Schizosaccharomyces pombe, RNAi is crucial to establish and maintain centromeric heterochromatin and functions to repress genome activity by a chromatin silencing mechanism referred to as co-transcriptional gene silencing (CTGS). Mechanistic details and the physiological relevance of CTGS are unknown. Here we show that RNAi components interact with chromatin at nuclear pores to keep stress response genes in check. We demonstrate that RNAi-mediated CTGS represses stress inducible genes by degrading mRNAs under non-induced conditions. Under chronic heat stress conditions, a Dicer thermoswitch deports Dicer to the cytoplasm, thereby disrupting CTGS and enabling expression of genes implicated in the acquisition of thermotolerance. Taken together, our work highlights a role for nuclear pores and the stress response transcription factor Atf1 in coordinating the interplay between the RNAi machinery and the S. pombe genome and uncovers a novel mode of RNAi regulation in response to an environmental cue. Total RNA extracted from wild-type and mutant strains to compare global expression. At least 2 biological replicates for each sample were performed.
Project description:RNA interference (RNAi) pathways are prevalent throughout the eukaryotic kingdom and well known to regulate gene expression on a post-transcriptional level in the cytoplasm. Less is known about possible functions of RNAi in the nucleus. In the fission yeast Schizosaccharomyces pombe, RNAi is crucial to establish and maintain centromeric heterochromatin and functions to repress genome activity by a chromatin silencing mechanism referred to as co-transcriptional gene silencing (CTGS). Mechanistic details and the physiological relevance of CTGS are unknown. Here we show that RNAi components interact with chromatin at nuclear pores to keep stress response genes in check. We demonstrate that RNAi-mediated CTGS represses stress inducible genes by degrading mRNAs under non-induced conditions. Under chronic heat stress conditions, a Dicer thermoswitch deports Dicer to the cytoplasm, thereby disrupting CTGS and enabling expression of genes implicated in the acquisition of thermotolerance. Taken together, our work highlights a role for nuclear pores and the stress response transcription factor Atf1 in coordinating the interplay between the RNAi machinery and the S. pombe genome and uncovers a novel mode of RNAi regulation in response to an environmental cue.
Project description:RNA interference (RNAi) pathways are prevalent throughout the eukaryotic kingdom and well known to regulate gene expression on a post-transcriptional level in the cytoplasm. Less is known about possible functions of RNAi in the nucleus. In the fission yeast Schizosaccharomyces pombe, RNAi is crucial to establish and maintain centromeric heterochromatin and functions to repress genome activity by a chromatin silencing mechanism referred to as co-transcriptional gene silencing (CTGS). Mechanistic details and the physiological relevance of CTGS are unknown. Here we show that RNAi components interact with chromatin at nuclear pores to keep stress response genes in check. We demonstrate that RNAi-mediated CTGS represses stress inducible genes by degrading mRNAs under non-induced conditions. Under chronic heat stress conditions, a Dicer thermoswitch deports Dicer to the cytoplasm, thereby disrupting CTGS and enabling expression of genes implicated in the acquisition of thermotolerance. Taken together, our work highlights a role for nuclear pores and the stress response transcription factor Atf1 in coordinating the interplay between the RNAi machinery and the S. pombe genome and uncovers a novel mode of RNAi regulation in response to an environmental cue.
Project description:Here we present the study on ChIP-chip mapping of the genomic binding sites for Sty1, Atf1, and the Atf1's binding partner Pcr1; the genome-wide transcriptional profiling of the atf1 and pcr1 strains in response to H2O2; and the phenotypic assessment of ~90 Atf1/Pcr1-bound or unbound genes for growth fitness under H2O2 conditions. ChIP-chip analysis shows that Atf1 and Pcr1 binding sites are overlapped in the genome and constitutively present before H2O2 stress. On the other hand, Sty1 recruitment primarily occurs at the Atf1/Pcr1 binding sites and is induced by H2O2. We found that Atf1/Pcr1 is clearly responsible for the high-level transcriptional response to H2O2. Furthermore, phenotypic assessment indicates that among the H2O2-induced genes, Atf1/Pcr1-bound genes exhibit a higher likelihood of functional requirement for growth fitness under the stress condition than the Atf1/Pcr1-unbound genes do. Notably, we found that the Atf1/Pcr1-bound genes regardless of their responsiveness to H2O2 show a high probability of requirement for growth fitness. . Expression level of genes in triplicates at 0min (without stress) is compared with that at 10, 30, 60, and 120min after stress treatment. ChIP-chip analyses is done for Atf1-HA, pcr1-HA, sty1-HA, Sty1-HA allele in the atf1D or pcr1D background without and with H2O2 (0.5mM for 30min).
Project description:Here we present the study on ChIP-chip mapping of the genomic binding sites for Sty1, Atf1, and the Atf1's binding partner Pcr1; the genome-wide transcriptional profiling of the atf1 and pcr1 strains in response to H2O2; and the phenotypic assessment of ~90 Atf1/Pcr1-bound or unbound genes for growth fitness under H2O2 conditions. ChIP-chip analysis shows that Atf1 and Pcr1 binding sites are overlapped in the genome and constitutively present before H2O2 stress. On the other hand, Sty1 recruitment primarily occurs at the Atf1/Pcr1 binding sites and is induced by H2O2. We found that Atf1/Pcr1 is clearly responsible for the high-level transcriptional response to H2O2. Furthermore, phenotypic assessment indicates that among the H2O2-induced genes, Atf1/Pcr1-bound genes exhibit a higher likelihood of functional requirement for growth fitness under the stress condition than the Atf1/Pcr1-unbound genes do. Notably, we found that the Atf1/Pcr1-bound genes regardless of their responsiveness to H2O2 show a high probability of requirement for growth fitness. .
Project description:The high osmolarity glycerol response (HOG) pathway plays a pivotal role in the stress response, virulence regulation, and differentiation of fungi, including Cryptococcus neoformans that causes fatal meningoencephalitis. Core signaling components of in the HOG pathway, including the Tco-Ypd1-Ssk1 phosphorelay system and the Ssk2-Pbs2-Hog1 MAPK module, have been elucidated but its downstream transcription factors remain unclear. Here we demonstrated that Atf1 with a basic leucine zipper domain is the transcription factor downstream of Hog1 in C. neoformans. We found that ATF1 expression was differentially regulated by oxidative damaging agents, mainly in a Hog1-dependent, but Mpk1-independent, manner. Interestingly, Atf1 not only promoted oxidative stress response and adaptation, but also played an opposing role to Hog1 in the process. Atf1 primarily localized to the nucleus under both unstressed and oxidative stress conditions in a Hog1-independent manner. Our data demonstrated that Atf1 promoted pheromone production and sexual differentiation under negative control by Hog1. Finally, a DNA microarray-based transcriptome analysis of the atf1∆ mutant under unstressed and oxidative stress conditions revealed that Atf1 regulated oxidative stress response genes, including a sulfiredoxin gene (SRX1). Intriguing, the array data further demonstrated that Atf1 modulated basal expression of genes involved in DNA repair and genotoxic stress response. Supporting this, we found that the atf1∆ mutant was highly sensitive to genotoxic agents. In conclusion, this study provided a further insight into the Hog1-dependent oxidative and genotoxic stress response and differentiation mechanism of C. neoformans.
Project description:The MAP kinase Sty1 of fission yeast accumulates in the nucleus upon stress, and stimulates expression of hundreds of genes, including atf1, via the constitutively nuclear transcription factor Atf1. The role on transcription of the signal-dependent phosphorylation of Atf1 by Sty1 is unclear. We have expressed the transcription factor and mutant derivatives from a constitutive promoter, to unchain Atf1 activity from its protein levels. Expression of a non-phosphorylatable Atf1 renders cells sensitive to oxidative stress, due to the impaired transcription of a subset of genes, those dependent on another transcription factor, Pap1. Cells expressing a phospho-mimicking mutant display enhanced resistance to stress, and while expression of the Pap1-dependent genes is still stress-dependent, a second subset of genes is constitutively expressed. Our study demonstrates that phosphorylation of Atf1 by Sty1 does not stimulate binding of the transcription factor to DNA but rather establishes a platform of interaction with the transcriptional machinery.
Project description:The high osmolarity glycerol response (HOG) pathway plays a pivotal role in the stress response, virulence regulation, and differentiation of fungi, including Cryptococcus neoformans that causes fatal meningoencephalitis. Core signaling components of in the HOG pathway, including the Tco-Ypd1-Ssk1 phosphorelay system and the Ssk2-Pbs2-Hog1 MAPK module, have been elucidated but its downstream transcription factors remain unclear. Here we demonstrated that Atf1 with a basic leucine zipper domain is the transcription factor downstream of Hog1 in C. neoformans. We found that ATF1 expression was differentially regulated by oxidative damaging agents, mainly in a Hog1-dependent, but Mpk1-independent, manner. Interestingly, Atf1 not only promoted oxidative stress response and adaptation, but also played an opposing role to Hog1 in the process. Atf1 primarily localized to the nucleus under both unstressed and oxidative stress conditions in a Hog1-independent manner. Our data demonstrated that Atf1 promoted pheromone production and sexual differentiation under negative control by Hog1. Finally, a DNA microarray-based transcriptome analysis of the atf1M-bM-^HM-^F mutant under unstressed and oxidative stress conditions revealed that Atf1 regulated oxidative stress response genes, including a sulfiredoxin gene (SRX1). Intriguing, the array data further demonstrated that Atf1 modulated basal expression of genes involved in DNA repair and genotoxic stress response. Supporting this, we found that the atf1M-bM-^HM-^F mutant was highly sensitive to genotoxic agents. In conclusion, this study provided a further insight into the Hog1-dependent oxidative and genotoxic stress response and differentiation mechanism of C. neoformans. There are more than 95% of genome homology between JEC21 and H99. Therefore 6 slides of JEC21 (Cryptococcus neoformans var. neoformans serotype D) 70-mer oligo are used in this analysis, 3 biological replicate experiments are performed, total RNAs are extracted 2 conditions (with or without treatment of Hydroten peroxide) from H99 (H99 Wild type strain (Cryptococcus neoformans var. grubii serotype A), and atf1M-NM-^T). We use the mixed all of total RNAs from this experiment as a control RNA. We use Cy3 as Sample dye and Cy5 as a control dye.