Programmed ribosomal frameshifting generates the Escherichia coli DNA polymerase III gamma subunit from within the tau subunit reading frame.
AUTOR(ES)
Blinkowa, A L
RESUMO
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 case 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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=330589Documentos Relacionados
- Translational frameshifting generates the gamma subunit of DNA polymerase III holoenzyme.
- The gamma subunit of DNA polymerase III holoenzyme of Escherichia coli is produced by ribosomal frameshifting.
- The adjacent dnaZ and dnaX genes of Escherichia coli are contained within one continuous open reading frame.
- DNA and RNA-DNA annealing activity associated with the tau subunit of the Escherichia coli DNA polymerase III holoenzyme.
- The Escherichia coli DNA polymerase III holoenzyme contains both products of the dnaX gene, tau and gamma, but only tau is essential.