The 3' end of drosophila histone H3 mRNA is produced by a processing activity in vitro.

We have examined the process by which the 3' terminus of the Drosophila histone H3 mRNA is produced in vitro. When a template containing a portion of DNA that flanks the normal 3' end of the histone H3 gene and an oligo dC tail on the template strand is transcribed in vitro by Drosophila RNA polymerase II, transcription continues beyond the 3' end of the H3 gene. A processing activity was identified that cleaves the precursor transcript generating an RNA species with the same 3' end as the mature H3 mRNA. The processing activity was partially purified by ion exchange chromatography and sucrose gradient sedimentation. The isolated activity was found to require Mg++ but did not require addition of a nucleoside triphosphate for activity. The activity sedimented with a molecular weight of approximately 140,000 daltons. Transcription of the template and processing of the RNA can be uncoupled in vitro.