Project description:The general pathways of eukaryotic mRNA decay occur via deadenylation followed by 3’ to 5’ degradation or decapping, although some endonuclease sites have been identified in metazoan mRNAs. To determine the role of endonucleases in mRNA degradation in Saccharomyces cerevisiae, we mapped 5’ monophosphate ends on mRNAs in wild-type and dcp2∆ xrn1∆ yeast cells, wherein mRNA endonuclease cleavage products are stabilized. This led to three important observations. First, only few mRNAs that undergo low level endonucleotyic cleavage were observed suggesting that endonucleases are not a major contributor to yeast mRNA decay. Second, independent of known decapping enzymes, we observed low levels of 5’ monophosphates on some mRNAs suggesting that an unknown mechanism can generate 5' exposed ends, although for all substrates tested Dcp2 was the primary decapping enzyme. Finally, we identified debranched lariat intermediates from intron-containing genes, demonstrating a significant discard pathway for mRNAs during the second step of pre-mRNA splicing, which is a potential new step to regulate gene expression.
Project description:We subjected yeast to two stresses, oxidative stress, which under current settings induces a fast and transient response in mRNA abundance, and DNA damage, which triggers a slow enduring response. Using microarrays, we performed a transcriptional arrest experiment to measure genome-wide mRNA decay profiles under each condition. Genome-wide decay kinetics in each condition were compared to decay experiments that were performed in a reference condition (only transcription inhibition without an additional stress) to quantify changes in mRNA stability in each condition. We found condition-specific changes in mRNA decay rates and coordination between mRNA production and degradation. In the transient response, most induced genes were surprisingly destabilized, while repressed genes were somewhat stabilized, exhibiting counteraction between production and degradation. This strategy can reconcile high steady-state level with short response time among induced genes. In contrast, the stress that induces the slow response displays the more expected behavior, whereby most induced genes are stabilized, and repressed genes destabilized. Our results show genome-wide interplay between mRNA production and degradation, and that alternative modes of such interplay determine the kinetics of the transcriptome in response to stress. Keywords: Four separate time courses
Project description:The general pathways of eukaryotic mRNA decay occur via deadenylation followed by 3’ to 5’ degradation or decapping, although some endonuclease sites have been identified in metazoan mRNAs. To determine the role of endonucleases in mRNA degradation in Saccharomyces cerevisiae, we mapped 5’ monophosphate ends on mRNAs in wild-type and dcp2∆ xrn1∆ yeast cells, wherein mRNA endonuclease cleavage products are stabilized. This led to three important observations. First, only few mRNAs that undergo low level endonucleotyic cleavage were observed suggesting that endonucleases are not a major contributor to yeast mRNA decay. Second, independent of known decapping enzymes, we observed low levels of 5’ monophosphates on some mRNAs suggesting that an unknown mechanism can generate 5' exposed ends, although for all substrates tested Dcp2 was the primary decapping enzyme. Finally, we identified debranched lariat intermediates from intron-containing genes, demonstrating a significant discard pathway for mRNAs during the second step of pre-mRNA splicing, which is a potential new step to regulate gene expression. 5' monophosphorylated ends of poly(A) RNA from wild-type and dcp2D xrn1D strains were identified in duplicates and triplicates, respectively.
Project description:Genome-wide mapping of decay factor-mRNA interactions in yeast identifies nutrient responsive transcripts as targets of the deadenylase Ccr4