Maintenance of cell fates through acetylated histone and the histone variant H2A.z in C. elegans

Maintenance of cell fates and regulation of the histone variant H3.3 by TLK kinase in Caenorhabditis elegans

Cell-fate maintenance is important to preserve the variety of cell types that are essential for the formation and function of tissues. We previously showed that the acetylated histone-binding protein BET-1 maintains cell fate by recruiting the histone variant H2A.z. Here, we report that Caenorhabditis elegans TLK-1 and the histone H3 chaperone CAF1 prevent the accumulation of histone variant H3.3. In addition, TLK-1 and CAF1 maintain cell fate by repressing ectopic expression of transcription factors that induce cell-fate specification. Genetic analyses suggested that TLK-1 and BET-1 act in parallel pathways. In tlk-1 mutants, the loss of SIN-3, which promotes histone acetylation, suppressed a defect in cell-fate maintenance in a manner dependent on MYST family histone acetyltransferase MYS-2 and BET-1. sin-3 mutation also suppressed abnormal H3.3 incorporation. Thus, we propose a hypothesis that the regulation and interaction of histone variants play crucial roles in cell-fate maintenance through the regulation of selector genes.

Summary: Histone H3 chaperone CAF1 maintains cell fate by repressing ectopic expression of genes for cell fate-specifying transcription factors. Accumulation of histone variant H3.3 correlates with defects in cell-fate maintenance.