Non-catalytic component of the MSL histone acetyltransferase complex, a multiprotein complex that mediates the majority of histone H4 acetylation at ‘Lys-16’ (H4K16ac), an epigenetic mark that prevents chromatin compaction (PubMed:16543150, PubMed:33837287). The MSL complex is required for chromosome stability and genome integrity by maintaining homeostatic levels of H4K16ac (PubMed:33837287). The MSL complex is also involved in gene dosage by promoting up-regulation of genes expressed by the X chromosome (By similarity). X up-regulation is required to compensate for autosomal biallelic expression (By similarity). The MSL complex also participates in gene dosage compensation by promoting expression of Tsix non-coding RNA (By similarity). MSL2 plays a key role in gene dosage by ensuring biallelic expression of a subset of dosage-sensitive genes, including many haploinsufficient genes (By similarity). Acts by promoting promoter-enhancer contacts, thereby preventing DNA methylation of one allele and creating a methylation-free environment for methylation-sensitive transcription factors such as SP1, KANSL1 and KANSL3 (By similarity). Also acts as an E3 ubiquitin ligase that promotes monoubiquitination of histone H2B at ‘Lys-35’ (H2BK34Ub), but not that of H2A (PubMed:21726816, PubMed:30930284). This activity is greatly enhanced by heterodimerization with MSL1 (PubMed:21726816, PubMed:30930284). H2B ubiquitination in turn stimulates histone H3 methylation at ‘Lys-4’ (H3K4me) and ‘Lys-79’ (H3K79me) and leads to gene activation, including that of HOXA9 and MEIS1 (PubMed:21726816). Also involved in the DNA damage response by mediating ubiquitination of TP53/p53 and TP53BP1 (PubMed:19033443, PubMed:23874665).
