G3 (Bethesda, Md.)Nov 28, 2014

The enzyme DIM-5 changes DNA packaging at the frequency gene and reduces its activation by light

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Apr 4, 2026

Abstract

DNA methylation at the frq promoter is dependent on both the DNA methyltransferase DIM-2 and the H3K9 methyltransferase DIM-5.

H3K9 trimethylation at frq peaks 30 minutes after light exposure.
Strains lacking dim-5 exhibit increased light-induced transcription and more White Collar-2 associated with the frq promoter.
Loss of H3K9 methylation leads to a phase advance in frq expression.
The dim-5 deletion strain shows increased circadian-regulated conidia formation.
A synthetic genetic interaction is observed between dim-5 and ras-1(bd).
DIM-5 may play a role in regulating circadian output by modulating light responsiveness.

Simplified

The transcriptional program controlling the circadian rhythm requires coordinated regulation of chromatin. Characterization of the chromodomain helicase DNA-binding enzyme CHD1 revealed DNA methylation in the promoter of the central clock gene frequency (frq) in Neurospora crassa. In this report, we show that the DNA methylation at frq is not only dependent on the DNA methyltransferase DIM-2 but also on the H3K9 methyltransferase DIM-5 and HP1. Histone H3 lysine 9 trimethylation (H3K9me3) occurs at frq and is most prominent 30 min after light-activated expression. Strains lacking dim-5 have an increase in light-induced transcription, and more White Collar-2 is found associated with the frq promoter. Consistent with the notion that DNA methylation assists in establishing the proper circadian phase, loss of H3K9 methylation results in a phase advance suggesting it delays the onset of frq expression. The dim-5 deletion strain displays an increase in circadian-regulated conidia formation on race tubes and there is a synthetic genetic interaction between dim-5 and ras-1(bd). These results indicate DIM-5 has a regulatory role in muting circadian output. Overall, the data support a model where facultative heterochromatic at frq serves to establish the appropriate phase, mute the light response, and repress circadian output.

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The enzyme DIM-5 changes DNA packaging at the frequency gene and reduces its activation by light

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