RNF4 regulates zebrafish granulopoiesis through the DNMT1-C/EBPα axis

RING finger protein 4 (RNF4) is a multifunctional small ubiquitin-related modifier (SUMO)-targeted ubiquitin E3 ligase (STUbL) ubiquitously expressed in all tissues, and which mainly participates in DNA repair and in chromatin and transcriptional regulation. Although RNF4 has been implicated in hematopoietic disorders, its ontogenic role during hematopoietic development remains undiscovered. We generated a zebrafish rnf4 knockout line by using transcription activator-like effector nucleases technology to address the impact of rnf4 during hematopoiesis. Rnf4-deficient zebrafish embryos exhibited sharply decreased neutrophils numbers during both primitive and definitive hematopoiesis. Mechanistic studies revealed that repression of the key granulocytic activator, CCAAT/enhancer-binding protein α ( c/ebpα), via promoter hypermethylation by SUMOylated DNA methyltransferase 1 (DNMT1) was the main cause of impaired granulopoiesis in rnf4-deficient zebrafish. In addition, for the first time, we identified DNMT1 as a potential new STUbL substrate of RNF4, with knockdown of dnmt1 largely restoring primitive and definitive granulopoiesis in rnf4-deficient zebrafish. Collectively, RNF4 is indispensable for zebrafish granulopoiesis through regulation of the DNMT1-C/EBPα functional axis.-Wang, L., Liu, X., Wang, H., Yuan, H., Chen, S., Chen, Z., de The, H., Zhou, J., Zhu, J. RNF4 regulates zebrafish granulopoiesis through the DNMT1-C/EBPα axis.