Programmed ribosomal frameshifting generates theEscherichia coliDNA polymerase III γ subunit from within the τ subunit reading frame
- 1 January 1990
- journal article
- research article
- Published by Oxford University Press (OUP) in Nucleic Acids Research
- Vol. 18 (7) , 1725-1729
- https://doi.org/10.1093/nar/18.7.1725
Abstract
The Escherichia coli dnaX gene encodes both the .tau. and .gamma. subunits of DNA polymerase III holoenzyme in one reading frame. The 71.1 kDa .tau. and the shorter .gamma. share N-terminal sequences. Mutagenesis of a potential ribosomal frameshift signal located at codons 428-430 without changing the amino acid sequence of the .tau. product, eliminated detectable synthesis of the .gamma. subunit, suggesting that the reading frame is shifted at that sequence and .gamma. is terminated by a nonsense codon located in the -1 frame 3 nucleotides downstream of the signal. This seems to be the first known cases of a frameshift which is used, along with the termination codon in the -1 frame, to terminate a peptide within a reading frame. [Mutagenesis of a dibasic peptide (lys-lys) at codons 498-499, the site at which a .tau.''-''LacZ fusion protein was cleaved in vitro (1) had no effect on .gamma. formation in vivo, suggesting that cleavage observed in vitro is not the mechanism of .gamma. formation in vivo.].Keywords
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