Natural antisense transcript of <i>Period2, Per2AS,</i> regulates the amplitude of the mouse circadian clock

Abstract

In mammals, a set of core clock genes form transcription-translation feedback loops to generate circadian oscillations. We and others recently identified a novel transcript at the <i>Period2</i> (<i>Per2</i>) locus that is transcribed from the antisense strand of <i>Per2</i> This transcript, <i>Per2AS,</i> is expressed rhythmically and antiphasic to <i>Per2</i> mRNA, leading to our hypothesis that <i>Per2AS</i> and <i>Per2</i> mutually inhibit each other's expression and form a double negative feedback loop. By perturbing the expression of <i>Per2AS</i>, we found that <i>Per2AS</i> transcription, but not transcript, represses <i>Per2</i> However, <i>Per2</i> does not repress <i>Per2AS,</i> as <i>Per2</i> knockdown led to a decrease in the <i>Per2AS</i> level, indicating that <i>Per2AS</i> forms a single negative feedback loop with <i>Per2</i> and maintains the level of <i>Per2</i> within the oscillatory range. <i>Per2AS</i> also regulates the amplitude of the circadian clock, and this function cannot be solely explained through its interaction with <i>Per2,</i> as <i>Per2</i> knockdown does not recapitulate the phenotypes of <i>Per2AS</i> perturbation. Overall, our data indicate that <i>Per2AS</i> is an important regulatory molecule in the mammalian circadian clock machinery. Our work also supports the idea that antisense transcripts of core clock genes constitute a common feature of circadian clocks, as they are found in other organisms.