The PIAS-like coactivator Zmiz1 directly and selectively coregulates Notch1 in T-cell development and leukemia [ChIP-Seq]

The most recurrently mutated oncogene in T-cell acute lymphoblastic leukemia (T-ALL) is NOTCH1. The core Notch complex consists of an ICN protein, a Maml cofactor, and the DNA binding factor Rbpj. The known direct cofactors of Notch appear to act nonselectively, homogeneously driving Notch gene expression functions. It is unclear whether there are direct cofactors of Notch that act selectively and heterogeneously regulate ICN. We discovered that Zmiz1, a Protein Inhibitor of Activated STAT (PIAS)-like coactivator, directly bound ICN1. In order to determine whether this interaction occured at chromatin, we performed ChIP-Seq. We identified significant overlap between ICN1, Rbpj, and Zmiz1 peaks. 75% of overlapping ICN1/Rbpj peaks overlapped with Zmiz1 (HA) peaks (273 peaks). The size of Zmiz1 (HA) peaks had moderate correlation with the size of Rbpj and ICN1 peaks. Like Rbpj and ICN1 peaks, Zmiz1 (HA) peaks were associated with activating H3K27ac, H3K4me1, and H3K4me3 chromatin marks and were devoid of repressive H3K27me3 marks. These data suggest that Zmiz1 is a selective Notch regulator. It co-binds only a subset of ICN1 and Rbpj-regulated sites. Overall design: Zmiz1, ICN1, Rbpj, histone mehylation ChIP-Seq in murine T-ALL cell line