By binding to ENY2, interferes with the nuclear functions of the deubiquitinase (DUB) module of the SAGA complex which consists of ENY2, ATXN7, ATXN7L3 and the histone deubiquitinating component USP22. Affects USP22 DUB activity toward histones indirectly by changing the subcellular distribution of ENY2 and altering ENY2 availability for ATXN7L3 interaction. Regulates H2B monoubiquitination (H2Bub1) levels through cytoplasmic sequestration of ENY2 resulting in loss of nuclear ENY2-ATXN7L3 association which destabilizes ATXN7L3. Affects protein expression levels of ENY2 and ATXN7L3. Interacts strongly with ENY2. Interacts weakly with USP22. A chromosomal aberration involving ATXN7L3B has been found in a mother and her two children with varying degrees of neurodevelopmental delay and cerebellar ataxia. One child also exhibits episodes of unresponsiveness suggestive of absence seizures and facial dysmorphism. Deletion at 12q21.1 deletes the entire single exon of ATXN7L3B. Encoded by an expressed retrotransposed copy of the ATXN7L3 locus that emerged prior to the speciation event separating primates and rodents. Belongs to the SGF11 family. Wrong choice of CDS.