Genome-wide binding of two new insulator-like proteins Pita and ZIPIC

Insulators are multiprotein–DNA complexes that regulate nuclear architecture. The Drosophila CP190 protein is a common cofactor of two main insulator complexes formed by the DNA-binding proteins Su(Hw) and dCTCF. Here, we have identified two new DNA-binding proteins, Pita and ZIPIC, that interact with CP190. In vitro, CP190 interacts with Pita through the BTB domain and with ZIPIC through the centrosomal targeting domain. The artificial binding sites for Pita or ZIPIC partially block enhancers and protect gene expression from PRE-mediated silencing in transgenic lines. Pita binds adjacent to dCTCF in the well-studied Mcp insulator and is required for its activity, which indicates that two insulator proteins can cooperate in organizing a functional insulator. Pita and ZIPIC preferentially bind to the promoter regions and extensively colocalize with dCTCF and BEAF. These results suggest that insulator proteins can fulfill multiple functions in chromosome architecture and gene expression. Overall design: ChIP-seq