Involved in histone pre-mRNA 3' processing and couples histone mRNA production with the cell cycle. Both maternal and zygotic proteins play an essential and vital function for development. Interacts with Sym and Cpsf73. In late embryos, expression is restricted to proliferating (CNS and PNS) and endoreplicating (midgut) cell populations. Expressed both zygotically and maternally. Expression is highest in early embryos and adult females. Belongs to the SLBP family.