Abstract: Objective To study the role of MDM2 in the ubiquitination of NOLC1, a regulator of MDM2. Methods Full-length NOLC1 proteins and its nuclear localization signal region were cloned and expressed in E.coli. Recombinant human MDM2 with ubiquitin ligase activity was used to study the ubiquitination of NOLC1 by MDM2 in in vitro ubiquitination system. The degradation of exogenous NOLC1 by MDM2 was studied in mammalian cells. Results MDM2 promoted the ubiquitination of full-length NOLC1 proteins and its Nuclear localization signal region in in vitro ubiquitination system. MDM2 promoted the proteasome dependent degradation of exogenous NOLC1 by over 70% in mammalian cells. Conclusion Ubiquitin ligase MDM2 promotes the ubiquitination and degradation of exogenous regulator NOLC1, which provides important clues for study the regulation of MDM2-TP53-NOLC1.

Key words: ubiquitin ligase, ubiquitination, MDM2, NOLC1