Autogenous regulation of the regA gene of bacteriophage T4: derepression of translation.
The regA gene of phage T4 encodes a translational repressor that inhibits utilization of its own mRNA as well as the translation of a number of other phage-induced mRNAs. In recombinant plasmids, autogenous translational repression limits production of the RegA protein when the cloned structural gene is expressed under control of a strong, plasmid-borne promoter (lambda PL). We have found that a genetic fusion which places the regA ribosome binding domain in proximity to active translation leads to partial derepression of wild-type RegA protein synthesis. The derepression is not due to increased synthesis of regA RNA, suggesting that it occurs at the translational level. Derepressed clones of the wild-type regA gene were used to overproduce and purify the repressor. In an in vitro assay the wild-type target was sensitive and a mutant target was resistant to inhibition by the added protein. The results suggest that the sensitivity of a regA-regulated cistron to translational repression may depend on the competition between ribosomes and RegA protein for overlapping recognition sequences in the translation initiation domain of the mRNA.
Liang
Y M
YM
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston 29425.
Wei
R X
RX
Hsu
T
T
Alford
C
C
Dawson
M
M
Karam
J
J
D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D005814:Genes, Viral; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D013604:T-Phages / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors