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HBO1 (MYST2/KAT7) is essential for histone 3 lysine 14 acetylation (H3K14ac), but is dispensable for H4 acetylation and DNA replication in mouse tissues. In contrast, previous studies using siRNA knockdown in human cell lines have suggested that HBO1 is essential for DNA replication. To determine if HBO1 has distinctly different roles in immortalized human cell lines compared to normal mouse cells, we performed siRNA knockdown of HBO1. In addition, we used CRISPR/Cas9 to generate 293T, MCF7 and HeLa cell lines lacking HBO1. Using both techniques, we show that HBO1 is essential for all H3K14ac in human cells and is unlikely to have a direct effect on H4 acetylation and only minor effects on cell proliferation. Surprisingly, loss of HBO1 and H3K14ac in HeLa cells led to the secondary loss of almost all H4 acetylation after 4 weeks. Thus, HBO1 is dispensable for DNA replication and cell proliferation in immortalized human cells. However, while cell proliferation proceeded without HBO1 and H3K14ac, HBO1 gene deletion lead to profound changes in cell adhesion, particularly in 293T cells. Consistent with this phenotype, loss of HBO1 in both 293T and HeLa principally affected genes mediating cell adhesion with comparatively minor effects on other cellular processes. [ABSTRACT FROM AUTHOR]

Acetylation of histone tails is a hallmark of transcriptionally active chromatin. Mof (males absent on the first; also called MYST1 or KAT8) is a member of the MYST family of histone acetyltransferases and was originally discovered as an essential component of the X chromosome dosage compensation system in Drosophila. In order to examine the role of Mof in mammals in vivo, we generated mice carrying a null mutation of the Mof gene. All Mof-deficient embryos fail to develop beyond the expanded blastocyst stage and die at implantation in vivo. Mof-deficient cell lines cannot be derived from Mof-/- embryos in vitro. Mof-/- embryos fail to acetylate histone 4 lysine 16 (H4K16) but have normal acetylation of other N-terminal histone lysine residues. Mof-/- cell nuclei exhibit abnormal chromatin aggregation preceding activation of caspase 3 and DNA fragmentation. We conclude that Mof is functionally nonredundant with the closely related MYST histone acetyltransferase Tip60. Our results show that Mof performs a different role in mammals from that in flies at the organism level, although the molecular function is conserved. We demonstrate that Mof is required specifically for the maintenance of H4K16 acetylation and normal chromatin architecture of all cells of early male and female embryos. [ABSTRACT FROM AUTHOR]

We report here that the MYST histone acetyltransferase HBO1 (histone acetyltransferase bound to ORC; MYST2/KAT7) is essential for postgastrulation mammalian development. Lack of HBO1 led to a more than 90% reduction of histone 3 lysine 14 (H3K14) acetylation, whereas no reduction of acetylation was detected at other histone residues. The decrease in H3K14 acetylation was accompanied by a decrease in expression of the majority of genes studied. However, some genes, in particular genes regulating embryonic patterning, were more severely affected than "housekeeping" genes. Development of HBO1-deficient embryos was arrested at the 10-somite stage. Blood vessels, mesenchyme, and somites were disorganized. In contrast to previous studies that reported cell cycle arrest in HBO1-depleted cultured cells, no defects in DNA replication or cell proliferation were seen in Hbo1 mutant embryo primary fibroblasts or immortalized fibroblasts. Rather, a high rate of cell death and DNA fragmentation was observed in Hbo1 mutant embryos, resulting initially in the degeneration of mesenchymal tissues and ultimately in embryonic lethality. In conclusion, the primary role of HBO1 in development is that of a transcriptional activator, which is indispensable for H3K14 acetylation and for the normal expression of essential genes regulating embryonic development. [ABSTRACT FROM AUTHOR]