Histone lysine demethylase JARID1a activates CLOCK-BMAL1 and influences the circadian clock
An enzyme that manages how DNA is packaged turns out to be part of the clock itself.
What this paper showed
Every cell keeps time using a loop of proteins that switch each other on and off over roughly twenty four hours. Two of them, CLOCK and BMAL1, act as the accelerator by turning clock genes on. Others act as the brake. The loop takes about a day to complete, which is where the daily rhythm comes from.
What this study added was the role of the DNA itself. Genes are not loose strands. They are wound around proteins called histones, and chemical marks on those histones decide how tightly the DNA is packed and therefore how easily a gene can be read. Enzymes add and remove those marks constantly.
One such enzyme, JARID1a, turned out to do more than housekeeping. It binds to CLOCK and BMAL1 and helps them keep clock genes switched on at the right point in the cycle. Remove it and the clock runs fast, completing its loop in less than a normal day.
This connected two fields that had been running separately. Chromatin biology, which studies how DNA is packaged and read, and circadian biology, which studies daily timing, turned out to be describing parts of the same machine. A number of independent research groups followed this line afterwards, and the link between the clock and the chemistry of the genome is now a standard part of how the field thinks.
