Project description:In Saccharomyces cerevisiae, the kinase Rio1 regulates rDNA transcription and segregation, pre-rRNA cleavage, and 40S ribosomal subunit maturation. Other roles are unknown. Human orthologue RIOK1; which is frequently overexpressed in malignancies, drives tumor growth and metastasis. Again, also RIOK1 biology is poorly understood. In this study, we charted the global activity of Rio1 in budding yeast. By producing and systems-integrating its protein-interaction, gene-transcription, and chromatin-binding maps we generated Rio1's multi-layered activity network, which controls protein synthesis and turnover, metabolism, growth, proliferation, and genetic stability. Rio1 regulates itself at the transcriptional level, and manages its network both directly and indirectly, via a battery of regulators and transcription factors, including Gcn4. We experimentally confirmed the network and show that Rio1 commands its downstream circuit depending on the growth conditions encountered. We also find that Rio1 and RIOK1 activities are functionally equivalent. Our data suggest that pathological RIOK1 expression may deregulate its network and fuel promiscuous transcription and ribosome production, uncontrolled metabolism, growth, proliferation, and chromosomal instability; well-known contributors to cancer initiation, maintenance and metastasis.
Project description:TATA-binding protein (TBP) nucleates the assembly of the transcription preinitiation complex (PIC), and although TBP can bind promoters with high stability in vitro, recent results establish that virtually the entire TBP population is highly dynamic in yeast nuclei in vivo. This dynamic behavior is surprising in light of models which posit that a stable TBP-containing scaffold facilitates transcription reinitiation at active promoters. The dynamic behavior of TBP is a consequence of the enzymatic activity of the essential Snf2/Swi2 ATPase Mot1, suggesting that ensuring a highly mobile TBP population is critical for transcriptional regulation on a global scale. Here high-resolution tiling arrays were used to define how perturbed TBP dynamics impact the precision of RNA synthesis in Saccharomyces cerevisiae. We find that Mot1 plays a broad role in establishing the precision and efficiency of RNA synthesis: in mot1-42 cells, RNA length changes were observed for 713 genes, about twice the number observed in set2∆ cells, which display a previously reported propensity for spurious initiation within open reading frames. Loss of Mot1 led to both aberrant transcription initiation and termination, with prematurely terminated transcripts representing the largest class of events. Genetic and genomic analyses support the conclusion that these effects on RNA length are mechanistically tied to dynamic TBP occupancies at certain types of promoters. These results suggest a new model whereby dynamic disassembly of the PIC can influence productive RNA synthesis.
Project description:Human BET family members are promising targets in the therapy of cancer and immunoinflammatory diseases, but their mechanism of action and functional redundancies are poorly understood. Yeast BET factors Bdf1/2 were previously proposed to act as anchors for coactivator TFIID. We investigated their genome wide roles in transcription and found that, while they cooperate with TFIID at many genes, their contributions to transcription are often significantly different. Bdf1/2 co-occupy the majority of yeast promoters and affect preinitiation complex formation by participating in recruitment of TFIID, Mediator and basal factors to chromatin. Surprisingly, we discovered that hypersensitivity of genes to Bdf1/2 depletion results from combined defects in initiation of transcription and early elongation. Bdf1/2 are critical components of yeast transcriptional machinery with many functional similarities to human BET proteins, most notably Brd4.