Component of the gypsy chromatin insulator complex which is required for the function of the gypsy chromatin insulator and other endogenous chromatin insulators. Chromatin insulators are regulatory elements which establish independent domains of transcriptional activity within eukaryotic genomes. Insulators have two defining properties; they can block the communication between an enhancer and a promoter when placed between them and can also buffer transgenes from position effect variegation (PEV). Insulators are proposed to structure the chromatin fiber into independent domains of differing transcriptional potential by promoting the formation of distinct chromatin loops. This chromatin looping may involve the formation of insulator bodies, where homotypic interactions between individual subunits of the insulator complex could promote the clustering of widely spaced insulators at the nuclear periphery. Within the gypsy insulator complex, this protein may directly bind to insulator DNA at sites distinct from those recognized by su(Hw). Required during embryogenesis for axial expansion, an actin/myosin dependent process that distributes the dividing nuclei along the anterior-posterior axis of the syncytial embryo. Does not appear to play a crucial role in organizing centrosomal microtubules during mitosis. Component of the gypsy chromatin insulator complex, composed of Cp190, mod(mdg4) and su(Hw) (PubMed:15574329). The gypsy chromatin insulator complex interacts with Topors via mod(mdg4) and su(Hw) (PubMed:15574329). Interacts with Cp60 and microtubules (PubMed:8590797, PubMed:9700165, PubMed:8491775, PubMed:8522588, PubMed:14996941). Interacts with inv (PubMed:25561495). Interacts with Nup98 (PubMed:28366641). Nucleus in interphase. Colocalizes with other elements of the gypsy chromatin insulator complex at multiple sites on polytene chromosomes and at nuclear insulator bodies. Expressed in spermatids but not in mature spermatozoa. Localizes within the spermatids to a sheath of microtubules around the nucleus and to microtubules within the tail. Localizes to the centrosome throughout the nuclear division cycle in early syncytial embryos. Localization to the interphase nucleus is seen from nuclear cycle 9 onwards.