Enables several functions, including Hsp70 protein binding activity; RNA polymerase II C-terminal domain binding activity; and nucleic acid binding activity. Involved in several processes, including positive regulation of FACT complex assembly; protein localization to euchromatin; and regulatory ncRNA-mediated heterochromatin formation. Located in chromosome and nucleus. Colocalizes with polytene chromosome interband and polytene chromosome puff. Is expressed in several structures, including adult head; adult heart; embryonic/larval midgut primordium; ganglia; and gonad. Orthologous to human CBX1 (chromobox 1).