The translational regulator protein regA is encoded by the T4 bacteriophage and binds to a region of messenger RNA (mRNA) that includes the initiator codon. RegA is unusual in that it represses the translation of about 35 early T4 mRNAs but does not affect nearly 200 other mRNAs [1].

1: Crystal structure of the T4 regA translational regulator protein at 1.9 A resolution. Kang C, Chan R, Berger I, Lockshin C, Green L, Gold L, Rich A; Science 1995;268:1170-1173. PMID:7761833

2: Bacteriophage T4 regA protein binds to mRNAs and prevents translation initiation. Winter RB, Morrissey L, Gauss P, Gold L, Hsu T, Karam J; Proc Natl Acad Sci U S A 1987;84:7822-7826. PMID:3120177