Genome-wide mapping of SETMAR transposase binding sites in the human genome

SETMAR/Metnase is a naturally occurring fusion protein that consists of a histone-lysine methyltransferase domain and an HsMar1 transposase. To elucidate the biological role of SETMAR, it is crucial to identify genomic targets to which SETMAR specifically binds and link these sites to the regulation of gene expression. Herein, we mapped the genomic landscape of SETMAR in a near-haploid human leukemia cell line (HAP1) in order to identify on-target and off-target binding sites at high resolution and to elucidate their role in terms of gene expression. Our analysis revealed a perfect correlation between SETMAR and inverted tandem repeats (ITRs) of HsMar1 transposon remnants, which are considered as natural target sites for SETMAR chromosome binding. However, we did not detect any untargeted events at non-ITR sequences, calling into question previously proposed off-target binding sites. We identified sequence fidelity of the ITR motif as a key factor for determining the binding affinity of SETMAR for chromosomes, as higher ITR fidelity resulted in increased affinity for chromatin and stronger repression of SETMAR-bound gene loci. These associations highlight how SETMAR's chromatin binding fine-tune gene regulatory networks in human tumour cells. Overall design: ChIP-seq analysis on HAP1 haploid human cell line to map genomic landscape of SETMAR.