Probable cyclin-dependent protein kinase (CDK) inhibitor that functions as a repressor of mitosis in the endoreduplication cell cycle (By similarity). May inhibit CDKA-1/CYCD complexes during S-phase, preventing the re-initiation of DNA replication (PubMed:20706207). Interacts with CDKA-1 and D-type cyclins (PubMed:20706207).