Functional genomic analysis of the haploinsufficient tumor suppressor, CUX1

CUX1 is a homeodomain-containing transcription factor that is conserved, ubiquitous, and essential in vertebrates and invertebrates. CUX1 is mutated or deleted in high-risk myeloid neoplasms and solid tumors, resulting in haploinsufficiency and tumor growth. Here we provide the first analysis of endogenous, whole genome, CUX1 DNA binding. We demonstrate that CUX1 binds with transcriptional activators and cohesin at distal enhancers across three different human cell types. Haploinsufficiency of CUX1 altered the expression of a large number of genes, including cell cycle regulators, with concomitant increased cellular proliferation. Surprisingly, CUX1 occupancy decreased genome-wide in the haploinsufficient state, and binding site affinity did not correlate with differential gene expression. Instead, differentially expressed genes had multiple, low-affinity CUX1 binding sites, consistent with an analog model for CUX1 gene regulation. A machine-learning algorithm determined that chromatin accessibility, enhancer activity, and distance to the transcription start site are features of functional CUX1 DNA binding. Moreover, CUX1 is enriched at sites of DNA looping, and these loops connect CUX1 to the promoters of target genes. We propose that CUX1 is an analog transcription factor that regulates target genes through higher order genome architecture. Overall design: RNA-seq and ChIP-seq of CUX1 in the wildtype and haploinsufficient states in K562 cells