Members of this protein family are found in temperate phage and bacterial prophage regions. Members include the product of the rha gene of the lambdoid phage phi-80, a late operon gene. The presence of this gene interferes with infection of bacterial strains that lack integration host factor (IHF), which regulates the rha gene. It is suggested that Rha is a phage regulatory protein.

1: Extensive domain shuffling in transcription regulators of DNA viruses and implications for the origin of fungal APSES transcription factors. Iyer LM, Koonin EV, Aravind L; Genome Biol 2002;3:RESEARCH0012. PMID:11897024