Ectopically tethered CP190 induces large-scale chromatin decondensation

Insulator mediated alteration in higher-order chromatinand/or nucleosomeorganization is an important aspect of epigenetic gene regulation. Recent studies have suggested a key role for CP190 in such processes. In this study, we analysed the effects of ectopically tethered insulator factors on chromatinstructure and found that CP190 induces large-scale decondensation when targeted to a condensed lacO array in mammalian and Drosophila cells. In contrast, dCTCF alone, is unable to cause such a decondensation, however, when CP190 is present, dCTCF recruits it to the lacO array and mediates chromatinunfolding. The CP190 induced opening of chromatinmay not be correlated with transcriptional activation, as binding of CP190 does not enhance luciferase activity in reporter assays. We propose that CP190 may mediate histone modification and chromatin remodellingactivity to induce an open chromatinstate by its direct recruitment or targeting by a DNA binding factor such as dCTCF.