The Absence of Functional CAF-1 Results in Deficiencies in H3.3 Levels at Transcribed Loci in Arabidopsis.

Eukaryotic organisms organize their genetic material in chromatin rather than naked DNA. Efficient chromatin assembly is essential for all DNA-templated processes, including replication, transcription, and DNA repair. Our research focused on two major histone H3 deposition complexes: Chromatin Assembly Factor (CAF-1) and Histone Regulator A (HIRA). CAF-1 deposits canonical H3 on naked DNA immediately after replication during the S-phase in yeast and metazoans, and HIRA is thought to incorporate the H3.3 variant in a replication-independent manner. By combining biochemical, genetic, genomic, and proteomic data, we revealed that CAF-1 activity might be associated with the maintenance of the histone variant H3.3 in Arabidopsis chromatin. Moreover, this CAF-1's potential function in H3.3 homeostasis may be particularly significant in the transcribed regions of the genome.