Rabbit Anti-Human RNF20 Polyclonal Antibody

Background: Ubiquitin conjugation and deconjugation on histone H2B regulate transcription and pre-mRNA splicing. Results: The splicing factor SART3 binds histones and enhances deubiquitination of H2B by the deubiquitinating enzyme, Usp15. Conclusion: SART3 is a dedicated histone chaperone that cooperates with Usp15 to deubiquitinate free histones. Significance: The coordinated activities of Usp15 and SART3 provide a link between H2B deubiquitination and pre-mRNA splicing. Post-translational modifications of histone proteins produce dynamic signals that regulate the structure and function of chromatin. Mono-ubiquitination of H2B in the histone tail (at Lys-123 in yeast or Lys-120 in humans) is a conserved modification that has been implicated in the regulation of transcription, replication, and DNA repair processes. In a search for direct effectors of ubH2B, we identified a deubiquitinating enzyme, Usp15, through affinity purification with a nonhydrolyzable ubH2B mimic. In the nucleus, Usp15 indirectly associates with the ubH2B E3 ligase, RNF20/RNF40, and directly associates with a component of the splicing machinery, SART3 (also known as TIP110 or p110). These physical interactions place Usp15 in the vicinity of actively transcribed DNA. Importantly we found that SART3 has previously unrecognized histone chaperone activities. SART3, but not the well-characterized histone chaperone Nap1, enhances Usp15 binding to ubH2B and facilitates deubiquitination of ubH2B in free histones but not in nucleosomes. These results suggest that SART3 recruits ubH2B, which may be evicted from DNA during transcription, for deubiquitination by Usp15. In light of the function played by SART3 in U4/U6 di-snRNP formation, our discovery points to a direct link between eviction-coupled erasure of the ubiquitin mark from ubH2B and co-transcriptional pre-mRNA splicing.

Zscan4 is an early embryonic gene cluster expressed in mouse embryonic stem and induced pluripotent stem cells where it plays critical roles in genomic stability, telomere maintenance, and pluripotency. Zscan4 expression is transient, and characterized by infrequent high expression peaks that are quickly down-regulated, suggesting its expression is tightly controlled. However, little is known about the protein degradation pathway responsible for regulating the human ZSCAN4 protein levels. In this study we determine for the first time the ZSCAN4 protein half-life and degradation pathway, including key factors involved in the process, responsible for the regulation of ZSCAN4 stability. We demonstrate lysine 48 specific polyubiquitination and subsequent proteasome dependent degradation of ZSCAN4, which may explain how this key factor is efficiently cleared from the cells. Importantly, our data indicate an interaction between ZSCAN4 and the E3 ubiquitin ligase RNF20. Moreover, our results show that RNF20 depletion by gene knockdown does not affect ZSCAN4 transcription levels, but instead results in increased ZSCAN4 protein levels. Further, RNF20 depletion stabilizes the ZSCAN4 protein half-life, suggesting that RNF20 negatively regulates ZSCAN4 stability. Due to the significant cellular functions of ZSCAN4, our results have important implications in telomere regulation, stem cell biology, and cancer. (C) 2018 The Authors. Published by Elsevier Inc.