Broad domains of histone marks in the highly compact Paramecium macronuclear genome
The Simon group recently published a new paper on gene regulation in Paramecium (full text pdf).
The unicellular ciliate Paramecium contains a large vegetative macronucleus with several unusual characteristics, including an extremely high coding density and high polyploidy. As macronuclear chromatin is devoid of heterochromatin, their study characterizes the functional epigenomic organization necessary for gene regulation and proper Polymerase II activity.
Their data imply that unoccupied DNA is the default state, whereas gene activation requires nucleosome recruitment together with broad domains of histone marker H3K4me3. Their findings on gene activation and silencing in Paramecium run counter to the current understanding of chromatin biology and may add a new aspect to its understanding.
