BMAL1 (ARNTL) contains both a nuclear localization signal and a nuclear export signal. The shuttling of BMAL1 between the nucleus and cytoplasm is important for transactivation by BMAL1:CLOCK/NPAS2 and degradation of BMAL1:CLOCK/NPAS2. BMAL1 initially forms a heterodimer with CLOCK or NPAS2 in the cytosol. The heterodimer is then phosphorylated and translocated into the nucleus.
