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SIR proteins create compact heterochromatin fibers
- Source :
- Proceedings of the National Academy of Sciences. 115:12447-12452
- Publication Year :
- 2018
- Publisher :
- Proceedings of the National Academy of Sciences, 2018.
-
Abstract
- SummaryHeterochromatin is a silenced chromatin region essential for maintaining genomic stability and driving developmental processes. The complicated structure and dynamics of heterochromatin have rendered it difficult to characterize. In budding yeast, heterochromatin assembly requires the SIR proteins -- Sir3, believed to be the primary structural component of SIR heterochromatin, and the Sir2/4 complex, responsible for the targeted recruitment of SIR proteins and the deacetylation of lysine 16 of histone H4. Previously, we found that Sir3 binds but does not compact nucleosomal arrays. Here we reconstitute chromatin fibers with the complete complement of SIR proteins and use sedimentation velocity, molecular modeling, and atomic force microscopy to characterize the stoichiometry and conformation of SIR chromatin fibers. In contrast to previous studies, our results demonstrate that SIR arrays are highly compact. Strikingly, the condensed structure of SIR heterochromatin fibers requires both the integrity of H4K16 and an interaction between Sir3 and Sir4. We propose a model in which two molecules of Sir3 bridge and stabilize two adjacent nucleosomes, while a single Sir2/4 heterodimer binds the intervening linker DNA, driving fiber compaction.
- Subjects :
- 0301 basic medicine
Heterochromatin
Saccharomyces cerevisiae
Histones
Histone H4
03 medical and health sciences
0302 clinical medicine
Gene Expression Regulation, Fungal
Nucleosome
Heterochromatin assembly
Silent Information Regulator Proteins, Saccharomyces cerevisiae
030304 developmental biology
0303 health sciences
Multidisciplinary
Chemistry
SIR proteins
Biological Sciences
Linker DNA
Heterotetramer
Cell biology
Chromatin
030104 developmental biology
Acetylation
Biophysics
030217 neurology & neurosurgery
Protein Binding
Subjects
Details
- ISSN :
- 10916490 and 00278424
- Volume :
- 115
- Database :
- OpenAIRE
- Journal :
- Proceedings of the National Academy of Sciences
- Accession number :
- edsair.doi.dedup.....411e802e8e12238c3bf826bc3097d74d
- Full Text :
- https://doi.org/10.1073/pnas.1810647115