4S oop RNA is a leader sequence for the immunity-establishment transcription in coliphage λ

Abstract
oop RNA, which is initiated at the po promoter and is 81 nucleotides long, can function as a leader sequence for the λ immunity establishment transcription, previously believed to originate at a special promoter pre located in the y region. Thus, oop RNA seems to have a dual role, either favouring the lytic cycle as a primer for the initiation of λ DNA replication, or leading to the establishment of lysogeny when elongated into the imm transcript, which directs synthesis of the repressor.