May function as a transcriptional corepressor through its interaction with COPS2, negatively regulating the expression of genes involved in neuronal differentiation. Homodimer (By similarity). Interacts with COPS2 (PubMed:12522100). Interacts with THOC7 (PubMed:12951069). Interaction with COPS2 may regulate localization to the nucleus. Ubiquitous. Detected in all tissues tested with higher expression in cerebellum, heart and kidney and to a lower level in cerebrum, lung, liver, spleen and muscle. Expressed in the developing brain from 10.5 dpc until 14.5 dpc. The expression decreases after 16.5 dpc, but an up-regulation is observed at P5 and the expression remains constant thereafter. Belongs to the GTP cyclohydrolase I type 2/NIF3 family.