Prp40 localizes to the histone locus body and regulates gene transcription and development.

In eukaryotes, a large amount of histones need to be synthesized during the S phase of the cell cycle to package newly synthesized DNA into chromatin. The transcription and 3' end processing of histone pre-mRNAs are controlled by the histone locus body (HLB), which is assembled on the shared promoter for and Here, we identified the Prp40 pre-mRNA processing factor (dPrp40, annotated as CG3542) as a novel HLB component. We showed that dPrp40 is essential for development, with functionally conserved activity in vertebrates and invertebrates. We observed that dPrp40 is fundamental in endocycling cells, highlighting a role for this factor in mediating replication efficiency The depletion of dPrp40 from fly cells inhibited the transcription, but not the 3' end processing, of histone mRNA in a - and -promoter-dependent manner. Our results establish that dPrp40 is an essential protein for development that can localize to the HLB and might participate in histone mRNA biosynthesis.