Description:
<jats:title>Significance</jats:title>
<jats:p>
Circadian oscillators rely on transcriptional negative feedback loops. In
<jats:italic>Drosophila</jats:italic>
, the key transcriptional repressor PERIOD (PER) slowly accumulates during the night under the control of its partner TIMELESS (TIM). A large number of posttranslational mechanisms regulate PER and TIM stability, but no mechanisms affecting the stability of their transcripts have been described. mRNA stability depends on the length of the poly(A) tail. We show that a deadenylase, POP2, shortens
<jats:italic>tim</jats:italic>
mRNA poly(A) tail, thus decreasing
<jats:italic>tim</jats:italic>
mRNA and TIM protein levels. Moreover, POP2 activity on
<jats:italic>tim</jats:italic>
mRNA appears to be inhibited by PER itself. These results reveal polyadenylation control of a core clock gene transcript and suggest that the repressor of the feedback loop also acts as a posttranscriptional regulator.
</jats:p>