ChIP-seq of TIP60 complex

Genome-wide mapping of TIP60 complex subunits in K562 cells. The objectives of this study are to describe TIP60 genome wide localization, confirm MBTD1 co-localization with already known unique subunits and observe the impact of MBTD1 on TIP60 complex targeting to chromatin. The TIP60 acetyltransferase complex is a key regulator of genome expression and stability. Here, we identified MBTD1 as a new stable subunit of the complex and revealed interesting insights about TIP60 function during the repair of DNA double strand breaks. MBTD1 binds H4K20me1/2, helping TIP60 association to specific promoters but also the DNA repair process by homologous recombination. While pro-end joining factor 53BP1 engages chromatin through simultaneous binding of H4K20me2 and H2AK15ub, TIP60 regulates the resolution of 53BP1 foci after DNA damage through a related bivalent mechanism. MBTD1 competes with 53BP1 for the H4K20me2 mark, affecting its retention at the break cooperatively with H4 acetylation by TIP60. In addition, we show that H2AK15ub deposition by RNF168 inhibits chromatin acetylation by TIP60, whereas H2AK15 can also be acetylated by TIP60 in vivo, therefore blocking its ubiquitylation. Altogether, these results uncover an intricate mechanism orchestrated by the TIP60 complex to regulate 53BP1-dependent repair pathway selection, through incompatible bivalent binding/action on chromatin. Chromatin immunoprecipitation was performed on K562 stable cell lines expressing 3xFLAG tagged TIP60 complex subunits integrated at AAVS1 locus. TIP60 complex genome wide localization is defined by the overlap of different subunits.