General coactivator that functions cooperatively with TAFs and mediates functional interactions between upstream activators and the general transcriptional machinery. Binds single-stranded DNA (By similarity). Binds specifically to the NssBF element, a short nucleotide sequence of the 1731 retrotransposon, to repress promoter activity. Expressed both maternally and zygotically, no expression is seen in larvae and weak expression in pupae. Belongs to the transcriptional coactivator PC4 family.