Essential histone chaperones collaborate to regulate transcription and chromatin integrity
- Olga Viktorovskaya1,
- James Chuang1,3,
- Dhawal Jain2,
- Natalia I. Reim1,
- Francheska López-Rivera1,
- Magdalena Murawska1,4,
- Dan Spatt1,
- L. Stirling Churchman1,
- Peter J. Park2 and
- Fred Winston1
- 1Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts 02115, USA;
- 2Department of Biomedical Informatics, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
- Corresponding author: winston{at}genetics.med.harvard.edu
Abstract
Histone chaperones are critical for controlling chromatin integrity during transcription, DNA replication, and DNA repair. Three conserved and essential chaperones, Spt6, Spn1/Iws1, and FACT, associate with elongating RNA polymerase II and interact with each other physically and/or functionally; however, there is little understanding of their individual functions or their relationships with each other. In this study, we selected for suppressors of a temperature-sensitive spt6 mutation that disrupts the Spt6-Spn1 physical interaction and that also causes both transcription and chromatin defects. This selection identified novel mutations in FACT. Surprisingly, suppression by FACT did not restore the Spt6-Spn1 interaction, based on coimmunoprecipitation, ChIP, and mass spectrometry experiments. Furthermore, suppression by FACT bypassed the complete loss of Spn1. Interestingly, the FACT suppressor mutations cluster along the FACT-nucleosome interface, suggesting that they alter FACT-nucleosome interactions. In agreement with this observation, we showed that the spt6 mutation that disrupts the Spt6-Spn1 interaction caused an elevated level of FACT association with chromatin, while the FACT suppressors reduced the level of FACT-chromatin association, thereby restoring a normal Spt6-FACT balance on chromatin. Taken together, these studies reveal previously unknown regulation between histone chaperones that is critical for their essential in vivo functions.
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Footnotes
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Supplemental material is available for this article.
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Article published online ahead of print. Article and publication date are online at http://www.genesdev.org/cgi/doi/10.1101/gad.348431.121.
- Received March 4, 2021.
- Accepted March 30, 2021.
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