Mutational analysis of the lac regulatory region: second-site changes that activate mutant promoters.
AUTOR(ES)
Rothmel, R K
RESUMO
Second-site mutations that restored activity to severe lacP1 down-promoter mutants were isolated. This was accomplished by using a bacteriophage f1 vector containing a fusion of the mutant E. coli lac promoters with the structural gene for chloramphenicol acetyltransferase (CAT), so that a system was provided for selecting phage revertants (or pseudorevertants) that conferred resistance of phage-infected cells to chloramphenicol. Among the second-site changes that relieved defects in mutant lac promoters, the only one that restored lacP1 activity was a T----G substitution at position -14, a weakly conserved site in E. coli promoters. Three other sequence changes, G----A at -2, A----T at +1, and C----A at +10, activated nascent promoters in the lac regulatory region. The nascent promoters conformed to the consensus rule, that activity is gained by sequence changes toward homology with consensus sequences at the -35 and -10 regions of the promoter. However, the relative activities of some promoters cannot be explained solely by consideration of their conserved sequence elements.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=317869Documentos Relacionados
- Second-site revertants of the P1 copN22 copy mutant.
- Genetic analysis of second-site revertants of bacteriophage lambda integrase mutants.
- Second-Site Changes Affect Viability of Amphotropic/Ecotropic Chimeric Enveloped Murine Leukemia Viruses
- Identification of Second-Site Mutations That Enhance Release and Spread of Vaccinia Virus
- Long-range structural effects in a second-site revertant of a mutant dihydrofolate reductase.