The ubiquitin E3 ligase complex RNF20:RNF40 (also known as Bre1 in Saccharomyces cerevisiae) interacts with the PAF complex and the E2-ubiquitin conjugate UBE2A,B:Ubiquitin (RAD6:Ubiquitin in Saccharomyces cerevisiae) (Zhu et al. 2005, Kim et al. 2009, Hahn et al. 2012, Foglizzo et al. 2016). The complex binds nucleosomal histone H2B after which RNF20:RNF40 monoubiquitinates histone H2B (Zhu et al. 2005, Kim et al. 2009). RNF20:RNF40 also binds WAC, which targets RNF20:RNF40 to the RNA polymerase II complex and promotes monoubiquitination of histone H2B (Zhang and Yu 2011).