Carraro et al, Molecular Cell, April 2023. Formation and maintenance of H3K9me3 regions involve assembly of new nucleosomes from H3-H4 histone dimers that include H3.3 histone with K9me3 modification. Until now, my image of post translational modifications of histones in nucleosomes was that a mechanism brings a chromatin complex to a location in the chromatin and enzymes in this complex perform a modification. While this is perhaps true in most cases, Carraro et al. describe a different scenario: new nucleosomes are assembled from H3-H4 histone dimers that are pre-assembled by different chaperone complexes, and DAXX complex makes dimers with H3.3 variant with H3K9me3 modification. It may improve understanding of expression changes of genes involved in the chaperone pathways described by Carraro et al.
Jieun Jeong (정지은), Ph.D. 