Histone Variant macroH2A1.1 Enhances Nonhomologous End Joining-dependent DNA Double-strand-break Repair and Reprogramming Efficiency of Human iPSCs

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Authors	GIALLONGO Sebastiano REHAKOVA Daniela BIAGINI Tommaso LO RE Oriana RAINA Priyanka LOCHMANOVÁ Gabriela ZDRÁHAL Zbyněk RESNICK Igor PATA Pille PATA Illar MISTRIK Martin DE MAGALHAES Joao Pedro MAZZA Tommaso KOUTNÁ Irena VINCIGUERRA Manlio
Year of publication	2022
Type	Article in Periodical
Magazine / Source	Stem Cells
MU Faculty or unit	Faculty of Medicine
Citation
Web	https://academic.oup.com/stmcls/article/40/1/35/6511687?login=true
Doi	http://dx.doi.org/10.1093/stmcls/sxab004
Keywords	1; DNA damage; cell reprogramming; induced pluripotent stem cells
Description	DNA damage repair (DDR) is a safeguard for genome integrity maintenance. Increasing DDR efficiency could increase the yield of induced pluripotent stem cells (iPSC) upon reprogramming from somatic cells. The epigenetic mechanisms governing DDR during iPSC reprogramming are not completely understood. Our goal was to evaluate the splicing isoforms of histone variant macroH2A1, macroH2A1.1, and macroH2A1.2, as potential regulators of DDR during iPSC reprogramming. GFP-Trap one-step isolation of mtagGFP-macroH2A1.1 or mtagGFP-macroH2A1.2 fusion proteins from overexpressing human cell lines, followed by liquid chromatography-tandem mass spectrometry analysis, uncovered macroH2A1.1 exclusive interaction with Poly-ADP Ribose Polymerase 1 (PARP1) and X-ray cross-complementing protein 1 (XRCC1). MacroH2A1.1 overexpression in U2OS-GFP reporter cells enhanced specifically nonhomologous end joining (NHEJ) repair pathway, while macroH2A1.1 knock-out (KO) mice showed an impaired DDR capacity. The exclusive interaction of macroH2A1.1, but not macroH2A1.2, with PARP1/XRCC1, was confirmed in human umbilical vein endothelial cells (HUVEC) undergoing reprogramming into iPSC through episomal vectors. In HUVEC, macroH2A1.1 overexpression activated transcriptional programs that enhanced DDR and reprogramming. Consistently, macroH2A1.1 but not macroH2A1.2 overexpression improved iPSC reprogramming. We propose the macroH2A1 splicing isoform macroH2A1.1 as a promising epigenetic target to improve iPSC genome stability and therapeutic potential.
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