Minor splicing factor 65K/RNPC3 interacts with ANKRD11 and mediates HDAC3-regulated histone deacetylation and transcription

Pre-mRNA splicing is coupled with DNA- and other RNA-processing machineries in the nucleus to form multilayer networks for accurate regulation of gene expression. However, those established couplings are major spliceosome-related, whether the minor spliceosome is involved remains unclear. Here, we first identified a direct interaction between a minor-specific protein 65K/RNPC3 and the histone deacetylase HDAC3 cofactor ANKRD11 through affinity co-purification using Drosophila lysate. In vivo assays revealed that the head of both DmAnkrd11Δ/Δ and Dm65KΔ/Δ mutants exhibited increased histone acetylation at H3K9 and H4K5, consistent with the high level of ANKRD11 in the central nervous systems. We then found that the 65K-ANKRD11 interaction is conserved in human, in which the HsANKRD11 middle-stretched domain mediates Hs65K association with HDAC3. CUT&Tag assays demonstrated that HDAC3 and Hs65K synergistically bind on chromatin, and the knockdown of ANKRD11 simultaneously decreased their bindings at the same chromatin locations and also increased nearby acetylation of H3K9. Sequencing of mRNAs revealed that the deficiency of HsANKRD11 or Hs65K caused changes in gene expression correlated with their chromatin-binding changes of HDAC3 and Hs65K and the levels of H3K9ac. This study provides a novel strategy for the regulation of histone deacetylation and gene expression through a minor spliceosome-specific component.