Biology subjects

Spatt, D.

Publications and source records attributed to Spatt, D..

3 recordsLinked to original sources

bioRxiv2022

Suppressor mutations that make the essential transcription factor Spn1/Iws1 dispensable in Saccharomyces cerevisiae

Spn1/Iws1 is an essential eukaryotic transcription elongation factor that is conserved from yeast to humans as an integral member of the RNA polymerase II elongation complex. Several studies have shown that Spn1 functions as a histone chaperone to control transcription, RNA splicing, genome stability, and histone modifications. However, the precise role of Spn1 is not understood, and there is little understanding of why it is essential for viability. To address these issues, we have isolated eight suppressor mutations that bypass the essential requirement for Spn1 in Saccharomyces cerevisiae. Unexpectedly, the suppressors identify several functionally distinct complexes and activities, including the histone chaperone FACT, the histone methyltransferase Set2, the Rpd3S histone deacetylase complex, the histone acetyltransferase Rtt109, the nucleosome remodeler Chd1, and a member of the SAGA co-activator complex, Sgf73. The identification of these distinct groups suggests that there are multiple ways in which Spn1 bypass can occur, including changes in histone acetylation and alterations of other histone chaperones. Thus, Spn1 may function to overcome repressive chromatin by multiple mechanisms during transcription. Our results suggest that bypassing a subset of these functions allows viability in the absence of Spn1.

molecular biology↗

bioRxiv2020

Essential histone chaperones collaborate to regulate transcription and chromatin integrity

Histone chaperones are critical for controlling chromatin integrity during transcription, DNA replication, and DNA repair. We have discovered that the physical interaction between two essential histone chaperones, Spt6 and Spn1/Iws1, is required for transcriptional accuracy and nucleosome organization. To understand this requirement, we have isolated suppressors of an spt6 mutation that disrupts the Spt6-Spn1 interaction. Several suppressors are in a third essential histone chaperone, FACT, while another suppressor is in the transcription elongation factor Spt5/DSIF. The FACT suppressors weaken FACT-nucleosome interactions and bypass the requirement for Spn1, possibly by restoring a necessary balance between Spt6 and FACT on chromatin. In contrast, the Spt5 suppressor modulates Spt6 function in a Spn1-dependent manner. Despite these distinct mechanisms, both suppressors alleviate the nucleosome organization defects caused by disruption of the Spt6-Spn1 interaction. Taken together, we have uncovered a network in which histone chaperones and other elongation factors coordinate transcriptional integrity and chromatin structure.

genetics↗

bioRxiv2018

Spt6 is required for the fidelity of promoter selection

Spt6 is a conserved factor that controls transcription and chromatin structure across the genome. Although Spt6 is viewed as an elongation factor, spt6 mutations in Saccharomyces cerevisiae allow elevated levels of transcripts from within coding regions, suggesting that Spt6 also controls initiation. To address the requirements for Spt6 in transcription and chromatin structure, we have combined four genome-wide approaches. Our results demonstrate that Spt6 represses transcription initiation at thousands of intragenic promoters. We characterize these intragenic promoters, and find sequence features conserved with genic promoters. Finally, we show that Spt6 also regulates transcription initiation at most genic promoters and propose a model of initiation-site competition to account for this. Together, our results demonstrate that Spt6 controls the fidelity of transcription initiation throughout the genome and reveal the magnitude of the potential for expressing alternative genetic information via intragenic promoters.

genomics↗