Required for the translational activation of PER1 mRNA in response to circadian clock. Binds directly to the 3'-UTR of the PER1 mRNA. Interacts with TNPO3, which may mediate nuclear import of the protein. Expressed in the suprachiasmatic nucleus (SCN) (at protein level). Expressed in the suprachiasmatic nucleus (SCN). Accumulates according to a circadian rhythm in the SCN.