USP44 and neoplasm: A second distinct tumor suppressive function of USP44 is that it may play an important role in nucleotide excision repair (NER) by stabilizing DDB2; experiments in cell lines which were exposed to UVC radiation have shown that DDB2, a gene that plays role in NER mechanism, remains ubiquitin-free due to USP44 function until XPC (Xeroderma pigmentosum) arrives and its activity further exists for subsequent rounds of damage recognition [8].