Monocistronic and polycistronic bacteriophage T4 gene 23 messages.

We studied transcription of T4 late genes by in vitro translation of size-fractionated late RNA and by hybridization of T4 late RNA to plasmids containing identified T4 late genes. We identified mRNA species that coded for the late proteins gp10, gp18, gp21, gp22, gp23, and gp24. Functional mRNA's that coded for the early proteins gp32 and IPIII were also detected after fractionation of late RNA. As in preparations of early RNA, gene 32 message activity was present in two species of RNA, which had molecular weights of approximately 0.5 x 10(6) and 0.8 x 10(6), and IPIII message activity was present in multiple species of RNA. Gene 24 and gene 10 message activities migrated as single species that had approximate molecular weights of 0.5 x 10(6) and 1.2 x 10(6), respectively. mRNA activity for gp18 migrated heterogeneously. We detected multiple transcripts from gene 23 by in vitro translation and by hybridization of late RNA to plasmids containing genes 21 through 23. Both types of analysis indicated that the major gene 23 transcript had a molecular weight of 0.75 x 10(6). In addition, two gene 23 transcripts having molecular weights of about 1.0 x 10(6) and 1.3 x 10(6) were present; these RNA species also coded for gp21 and gp22. Physical linkage of transcripts from genes 21, 22, and 23 was demonstrated by hybridization.