Non-catalytic component of the NSL histone acetyltransferase complex, a multiprotein complex that mediates histone H4 acetylation at 'Lys-5'- and 'Lys-8' (H4K5ac and H4K8ac) at transcription start sites and promotes transcription initiation (PubMed:20018852, PubMed:33657400). The NSL complex also acts as a regulator of gene expression in mitochondria (PubMed:27768893). Within the NSL complex, KANSL3 is required to promote KAT8 association with mitochondrial DNA (PubMed:27768893). Required for transcription of intraciliary transport genes in both ciliated and non-ciliated cells (By similarity). This is necessary for cilium assembly in ciliated cells and for organization of the microtubule cytoskeleton in non-ciliated cells (By similarity). Also required within the NSL complex to maintain nuclear architecture stability by promoting KAT8-mediated acetylation of lamin LMNA (By similarity). Plays an essential role in spindle assembly during mitosis (PubMed:26243146). Acts as a microtubule minus-end binding protein which stabilizes microtubules and promotes their assembly (PubMed:26243146). Indispensable during early embryonic development where it is required for proper lineage specification and maintenance during peri-implantation development and is essential for implantation (By similarity). {ECO:0000250|UniProtKB:A2RSY1, ECO:0000269|PubMed:20018852, ECO:0000269|PubMed:26243146, ECO:0000269|PubMed:27768893, ECO:0000269|PubMed:33657400}. This is the function of ENSG00000114982 (KANSL3, KAT8 regulatory NSL complex subunit 3).