The protein encoded by this gene is highly similar to Nocturnin, a gene identified as a circadian clock regulated gene in Xenopus laevis. This protein and Nocturnin protein share similarity with the C-terminal domain of a yeast transcription factor, carbon catabolite repression 4 (CCR4). The mRNA abundance of a similar gene in mouse has been shown to exhibit circadian rhythmicity, which suggests a role for this protein in clock function or as a circadian clock effector. [provided by RefSeq, Jul 2008]