[The region of phage T4 W-29 genes: cloning and expression]

Abstract

The EcoRI fragment of T4 DNA containing the W-29 genes and its subfragments were cloned in the pBR322 and the singlestranded M13 phage. Hybridization with a cloned DNA showed that in T4 infected cells the transcription of the late genes 25-29 depends on the phage-induced RNA polymerase changes and on replication of phage DNA. At a late infection stage one also observes an enhanced transcription of the (early) genes uvsW and uvsY, which depends on viral DNA replication. Both early and late genes within recombinant plasmids are also expressed in uninfected cells carrying a plasmid regardless of the inserted fragment orientation and independently of the vector promoters. Hybrid plasmids demonstrated a high frequency of recombination with phage DNA in the infected cell. An RNA polymerase from uninfected cells binds itself to the late cloned genes to form "open" complexes. A purified RNA polymerase transcribes both early and late genes within recombinant plasmids. The relative transcription of the late cloned genes is enhanced if one uses an RNA polymerase from T4-infected cells. The super-helicity of template DNA is essential for transcription of early and late genes.