Facilitates ubiquitin-independent proteasomal degradation of polycomb protein CBX4 (By similarity). Plays a role in inhibiting the activity of glucokinase GCK and both glucose-induced and basal insulin secretion (PubMed:24187134). Interacts with glucokinase GCK; the interaction occurs preferentially at low glucose levels. Detected in the nucleus and nucleolus with no expression in the cytoplasm (By similarity). However, a later study finds expression in the nucleus and cytoplasm with no expression in the nucleolus (PubMed:24187134). Down-regulated at high glucose levels of 10 and 25 mmol/liter glucose with highest expression at low glucose levels of 3 mmol/liter.