Transcriptional repressor which may act as a negative-feedback regulator of CLOCK-ARNTL/BMAL1 transcriptional activity in the circadian-clock mechanism. May stimulate ARNTL/BMAL1-dependent phosphorylation of CLOCK. However, the physiogical relevance of these observations is unsure, since experiments in knockout mice showed that CIPC is not critially required for basic circadian clock.