The zinc-finger protein ZCCHC2 suppresses retinoblastoma tumorigenesis by inhibiting HectH9-mediated K63-linked polyubiquitination and activation of c-Myc

Retinoblastoma (RB) is the most common intraocular malignancy. The tumor propagation of RB is maintained by several core transcriptional regulators, including c-Myc. Strictly regulated posttranslational modifications control the c-Myc protein. However, the posttranslational regulatory mechanisms for c-Myc in retinoblastoma remain largely unclear. Here, we identified the zinc-finger protein ZCCHC2 as a critical negative regulator of c-Myc-associated tumorigenesis. Knockout of ZCCHC2 promoted retinoblastoma cell proliferation, whereas ZCCHC2 overexpression had the opposite effect. Meanwhile, the level of ZCCHC2 was positively correlated with retinoblastoma tumorigenesis and animal survival in vivo. Mechanistically, ZCCHC2 was associated with c-Myc and negatively regulated the K63-linked polyubiquitination of c-Myc. We demonstrated that ZCCHC2 inhibits the interaction of the E3 ubiquitin ligase HectH9 with c-Myc and that ZCCHC2 inhibits HectH9-mediated K63-linked polyubiquitination and activation of c-Myc. Altogether, these data suggest that ZCCHC2 plays a role in the regulation of RB tumorigenesis through the inhibition activity of c-Myc. (C) 2019 Published by Elsevier Inc.