Project description:During transcription initiation, the TFIIH-kinase Kin28/Cdk7 marks RNA polymerase II (Pol II) by phosphorylating the C-terminal domain (CTD) of its largest subunit. Here we describe a structure-guided chemical approach to covalently and specifically inactivate Kin28 kinase activity in vivo. This method of irreversible inactivation recapitulates both the lethal phenotype and the key molecular signatures that result from genetically disrupting Kin28 function in vivo. Inactivating Kin28 impacts promoter release to differing degrees and reveals a “checkpoint” during the transition to productive elongation. While promoter-proximal pausing is not observed in budding yeast, inhibition of Kin28 attenuates elongation-licensing signals, resulting in Pol II accumulation at the +2 nucleosome and reduced transition to productive elongation. Furthermore, upon inhibition, global stabilization of mRNA masks different degrees of reduction in nascent transcription. This study resolves long-standing controversies on the role of Kin28 in transcription and provides a rational approach to irreversibly inhibit other kinases in vivo.
Project description:Inhibition of Kin28/CDK7, the kinase subunit of TFIIH, leads to defects in transcription of protein-coding genes. Despite a severe reduction in nascent RNA synthesis, the majority of mRNAs retain their steady-state level upon inhibition. In this study, we examined the determinants of mRNA stability in cells experiencing transcriptional crisis via irreversible chemical inhibition of Kin28. We discovered that the inhibited Kin28 transcriptome resembles the transcriptome of cells treated with an inhibitor of protein synthesis. Indeed, inhibition of Kin28 induces a coordinated decrease in translation and an increase in P-body formation. Unexpectedly, integrated stress response effectors do not trigger the observed proteostasis and ribostasis. Rather, mRNAs that are buffered from degradation display a preference for Ski2 over Nab2 and are differentially sensitive to the 5′-exonuclease Xrn1. These findings reveal that a nuclear kinase, well-known for its role in early stages of RNA synthesis, orchestrates multiple molecular processes in different cellular compartments.
Project description:During transcription initiation, the TFIIH-kinase Kin28/Cdk7 marks RNA polymerase II (Pol II) by phosphorylating the C-terminal domain (CTD) of its largest subunit. Here we describe a structure-guided chemical approach to covalently and specifically inactivate Kin28 kinase activity in vivo. This method of irreversible inactivation recapitulates both the lethal phenotype and the key molecular signatures that result from genetically disrupting Kin28 function in vivo. Inactivating Kin28 impacts promoter release to differing degrees and reveals a “checkpoint” during the transition to productive elongation. While promoter-proximal pausing is not observed in budding yeast, inhibition of Kin28 attenuates elongation-licensing signals, resulting in Pol II accumulation at the +2 nucleosome and reduced transition to productive elongation. Furthermore, upon inhibition, global stabilization of mRNA masks different degrees of reduction in nascent transcription. This study resolves long-standing controversies on the role of Kin28 in transcription and provides a rational approach to irreversibly inhibit other kinases in vivo.
Project description:During transcription initiation, the TFIIH-kinase Kin28/Cdk7 marks RNA polymerase II (Pol II) by phosphorylating the C-terminal domain (CTD) of its largest subunit. Here we describe a structure-guided chemical approach to covalently and specifically inactivate Kin28 kinase activity in vivo. This method of irreversible inactivation recapitulates both the lethal phenotype and the key molecular signatures that result from genetically disrupting Kin28 function in vivo. Inactivating Kin28 impacts promoter release to differing degrees and reveals a â??checkpointâ?? during the transition to productive elongation. While promoter-proximal pausing is not observed in budding yeast, inhibition of Kin28 attenuates elongation-licensing signals, resulting in Pol II accumulation at the +2 nucleosome and reduced transition to productive elongation. Furthermore, upon inhibition, global stabilization of mRNA masks different degrees of reduction in nascent transcription. This study resolves long-standing controversies on the role of Kin28 in transcription and provides a rational approach to irreversibly inhibit other kinases in vivo. Total RNA was collected from wild-type and analog-sensitive Kin28 strains treated with reversible inhibitor 1-NAPP-1, irreversible inhibitor CMK, and solvent control DMSO. Equivalent ratios of S. pombe : S. cerevisiae cells were added to each sample before RNA extraction for normalization of read counts after sequencing. Nascent RNA was purified from total RNA by 4-thiouracil labeling, biotinylation, and streptavidin-pulldown. As a negative control, nascent RNA was also extracted from total RNA from cells that had not been treated with 4-thiouracil.
Project description:Whole genome analysis of total RNA pol II, Ser2-, Ser5- and Ser7-phosphorylated RNA pol II, in WT and mutants of the C-terminal domain (CTD) kinases Ctk1 and Kin28, and localization of the termination factors Pcf11, Nrd1 and Rat1.