Alternative titles; symbols
HGNC Approved Gene Symbol: RNF20
Cytogenetic location: 9q31.1 Genomic coordinates (GRCh38) : 9:101,533,853-101,563,344 (from NCBI)
Ubiquitination controls various cellular functions by tagging proteins for proteasomal degradation or incorporation into other regulatory complexes. Central to this system are E3 ubiquitin ligases, which function in the chain of reactions resulting in attachment of ubiquitin moieties to substrate proteins. RNF20 is the major E3 ubiquitin ligase responsible for monoubiquitination of histone H2B (see 609904). Ubiquitinated H2B is actively engaged in transcription and is involved in DNA damage repair in nuclear foci of DNA double-stranded breaks (summary by Blank et al., 2012).
Hwang et al. (2003) identified an S. cerevisiae protein, Bre1, as an evolutionarily conserved RING finger protein that is required in vivo for both ubiquitination of histone H2B and methylation of histone H3 (see 602810) on lys4. They identified 2 human homologs of Bre1, RNF20 and RNF40 (607700), which they termed BRE1A and BRE1B, respectively. The predicted RNF20 protein contains 523 amino acids and has a conserved RING finger domain at its C terminus.
Hwang et al. (2003) showed that the S. cerevisiae Bre1 protein is required in vivo for both H2B ubiquitination and H3 lys4 methylation. They determined that the RING domain of Bre1 is essential for both of these modifications, as is large-1 (Lge1), a protein required for cell size control that copurifies with Bre1. In cells lacking the euchromatin-associated histone variant H2A.Z, Bre1, Rad6 (see 312180), and Lge1 were each essential for cell viability, supporting redundant functions for H2B ubiquitination and H2A substitution in the formation of active chromatin. Analysis of mutants demonstrated a function for Bre1/Lge1-dependent H2B monoubiquitination in the control of cell size.
Wood et al. (2003) showed that the RING finger of S. cerevisiae Bre1 is required for ubiquitination of H2B, methylation of lys4 and lys79 of H3, and for telomeric silencing. Chromatin immunoprecipitation experiments indicated that both Rad6 and Bre1 are recruited to a promoter. The authors determined that Bre1 is essential for this recruitment of Rad6 and is dedicated to the transcriptional pathway of Rad6. The results suggested that Bre1 is the likely E3 enzyme that directs Rad6 to modify chromatin and ultimately to affect gene expression.
Kim et al. (2005) showed that human BRE1A is a nuclear protein that binds to histones in vitro and in vivo. BRE1A increased the global level of H2B ubiquitylation at lys120 and enhanced activator-dependent transcription. Reduction of BRE1A by RNA interference decreased endogenous H2B ubiquitylation, activator-dependent transcription, and H3 lys4 and lys79 methylation. BRE1A interacted with p53 (TP53; 191170) directly and was recruited to the MDM2 (164785) promoter in a p53-dependent manner. Kim et al. (2005) concluded that BRE1A is an H2B-specific E3 ubiquitin ligase that functions, through direct activator interactions, as a transcriptional coactivator.
Shema et al. (2008) found that knockdown of RNF20 in HeLa cells led to near complete ablation of H2B ubiquitylation, but it did not affect expression of the majority of genes. RNF20 knockdown also had no effect on cell cycle distribution. Genes downregulated by RNF20 knockdown included H2A, H2B, and p53, whereas several protooncogenes exhibited increased expression. RNF20 knockdown and EGF (131530) stimulation affected an overlapping set of genes, and the combination of EGF treatment and RNF knockdown had an additive effect on transcription. RNF20 knockdown also increased cell migration and elicited transformation and tumorigenesis. Analysis of 56 breast cancer DNA samples revealed statistically significant hypermethylation of the RNF20 promoter in a substantial number of tumors compared with normal tissue, suggesting that RNF20 possesses tumor suppressor function and that its downregulation promotes tumor formation.
Blank et al. (2012) found that knockdown of the HECT domain E3 ubiquitin ligase SMURF2 (605532) in human tumor cell lines resulted in increased levels of RNF20 protein and ubiquitinated H2B. Knockdown of RNF20 increased chromatin compaction. Immunohistochemical analysis of 40 breast cancer tissues and 55 lymphomas and matched adjacent normal tissue showed that tumor formation was associated with low SMURF2 expression and high RNF20 expression. Smurf2-null mouse embryonic fibroblasts showed elevated proliferation compared with wildtype and, particularly in later passages, evidence of DNA damage and enhanced ability to form tumors following injection into nude mice. These changes were associated with elevated Rnf20 protein, but not mRNA, relaxed chromatin compaction, and elevated ubiquitination of H2B. Knockdown of Rnf20 in Smurf2-null cells retarded cell growth and oncogenic transformation and reduced the amount of ubiquitinated H2B. Blank et al. (2012) concluded that SMURF2 is directly involved in regulation of the DNA damage response by directing polyubiquitination and proteasomal degradation of RNF20.
Using a CRISPR-based loss-of-function screen in mouse regulatory T cells (Tregs), Cortez et al. (2020) identified several modulators of Foxp3 (300292) expression, including the deubiquitinase Usp22 (612116) as a positive regulator of Foxp3, and the E3 ubiquitin ligase Rnf20 as a negative regulator. Treg-specific ablation of Usp22 in mice reduced Foxp3 protein levels and caused defects in Treg suppressive function, resulting in spontaneous autoimmunity and protection against tumor growth in multiple cancer models. Foxp3 destabilization in Usp22-deficient Tregs could be rescued by ablation of Rnf20, revealing a reciprocal ubiquitin switch in Tregs.
In a study of 1,751 knockout alleles created by the International Mouse Phenotyping Consortium (IMPC), Dickinson et al. (2016) found that knockout of the mouse homolog of human RNF20 is homozygous-lethal (defined as absence of homozygous mice after screening of at least 28 pups before weaning).
Blank, M., Tang, Y., Yamashita, M., Burkett, S. S., Cheng, S. Y., Zhang, Y. E. A tumor suppressor function of Smurf2 associated with controlling chromatin landscape and genome stability through RNF20. Nature Med. 18: 227-234, 2012. [PubMed: 22231558] [Full Text: https://doi.org/10.1038/nm.2596]
Cortez, J. T., Montauti, E., Shifrut, E., Gatchalian, J., Zhang, Y., Shaked, O., Xu, Y., Roth, T. L., Simeonov, D. R., Zhang, Y., Chen, S., Li, Z., and 13 others. CRISPR screen in regulatory T cells reveals modulators of Foxp3. Nature 582: 416-420, 2020. [PubMed: 32499641] [Full Text: https://doi.org/10.1038/s41586-020-2246-4]
Dickinson, M. E., Flenniken, A. M., Ji, X., Teboul, L., Wong, M. D., White, J. K., Meehan, T. F., Weninger, W. J., Westerberg, H., Adissu, H., Baker, C. N., Bower, L., and 73 others. High-throughput discovery of novel developmental phenotypes. Nature 537: 508-514, 2016. Note: Erratum: Nature 551: 398 only, 2017. [PubMed: 27626380] [Full Text: https://doi.org/10.1038/nature19356]
Hwang, W. W., Venkatasubrahmanyam, S., Ianculescu, A. G., Tong, A., Boone, C., Madhani, H. D. A conserved RING finger protein required for histone H2B monoubiquitination and cell size control. Molec. Cell 11: 261-266, 2003. [PubMed: 12535538] [Full Text: https://doi.org/10.1016/s1097-2765(02)00826-2]
Kim, J., Hake, S. B., Roeder, R. G. The human homolog of yeast BRE1 functions as a transcriptional coactivator through direct activator interactions. Molec. Cell 20: 759-770, 2005. [PubMed: 16337599] [Full Text: https://doi.org/10.1016/j.molcel.2005.11.012]
Shema, E., Tirosh, I., Aylon, Y., Huang, J., Ye, C., Moskovits, N., Raver-Shapira, N., Minsky, N., Pirngruber, J., Tarcic, G., Hublarova, P., Moyal, L., Gana-Weisz, M., Shiloh, Y., Yarden, Y., Johnsen, S. A., Vojtesek, B., Berger, S. L., Oren, M. The histone H2B-specific ubiquitin ligase RNF20/hBRE1 acts as a putative tumor suppressor through selective regulation of gene expression. Genes Dev. 22: 2664-2676, 2008. Note: Erratum: Genes Dev. 31: 1926 only, 2017. [PubMed: 18832071] [Full Text: https://doi.org/10.1101/gad.1703008]
Wood, A., Krogan, N. J., Dover, J., Schneider, J., Heidt, J., Boateng, M. A., Dean, K., Golshani, A., Zhang, Y., Greenblatt, J. F., Johnston, M., Shilatifard, A. Bre1, an E3 ubiquitin ligase required for recruitment and substrate selection of Rad6 at a promoter. Molec. Cell 11: 267-274, 2003. [PubMed: 12535539] [Full Text: https://doi.org/10.1016/s1097-2765(02)00802-x]