Characterisation of Myst2 and Niam interactomes in mouse embryonic stem cells

Here we undertake the characterisation of Myst2 protein interactions in mouse embryonic stem cells by affinity purification and mass spectrometry using a Myst2-FTAP tagged cell line. This protein interaction study confirms that in mouse embryonic stem cells Myst2 is part of H3 and H4 histone acetylation complexes similar to those described in somatic cells. We identify a novel Myst2- associated protein, the tumour suppressor protein Niam (Nuclear Interactor of Arf and Mdm2), and show that it also interacts with subunits of Myst2 H4 HAT complexes. Human NIAM is involved in chromosome segregation, p53 regulation and cell proliferation in somatic cells, but its role in embryonic stem cells is unknown. We describe the first Niam embryonic stem cell interactome, which includes proteins with roles in DNA replication and repair, transcription, splicing and ribosome biogenesis. Many of Myst2 and Niam binding partners are required for correct embryonic development, implicating Myst2 and NIAM in the cooperative regulation of this process and suggesting a novel role for Niam in embryonic biology. The data provides a useful resource for exploring Myst2 and Niam essential cellular functions and should contribute to deeper understanding of organism development and survival as well as the development of cancer.