Modulation of EcoKI restriction in vivo: role of the lambda Gam protein and plasmid metabolism.

AUTOR(ES)

Salaj-Smic, E

RESUMO

Two novel types of alleviation of DNA restriction by the EcoKI restriction endonuclease are described. The first type depends on the presence of the gam gene product (Gam protein) of bacteriophage lambda. The efficiency of plating of unmodified phage lambda is greatly increased when the restricting Escherichia coli K-12 host carries a gam+ plasmid. The effect is particularly striking in wild-type strains and, to a lesser extent, in the presence of sbcC and recA mutations. In all cases, Gam-dependent alleviation of restriction requires active recBCD genes of the host and recombination (red) genes of the infecting phage. The enhanced capacity of Gam-expressing cells to repair DNA strand breaks might account for this phenomenon. The second type is caused by the presence of a plasmid in a restricting host lacking RecBCD enzyme. Commonly used plasmids such as the cloning vector pACYC184 can produce such an effect in strains carrying recB single mutations or in recBC sbcBC strains. Plasmid-mediated restriction alleviation in recBC sbcBC strains is independent of the host RecF, RecJ, and RecA proteins and phage recombination functions. The presence of plasmids can also relieve restriction in recD strains. This effect depends, however, on the RecA function in the host. The molecular mechanism of the plasmid-mediated restriction alleviation remains unclear.

Documentos Relacionados

• Plasmid R16 ArdA Protein Preferentially Targets Restriction Activity of the Type I Restriction-Modification System EcoKI
• Interaction of the ocr gene 0.3 protein of bacteriophage T7 with EcoKI restriction/modification enzyme
• Translocation and specific cleavage of bacteriophage T7 DNA in vivo by EcoKI
• S-adenosyl methionine alters the DNA contacts of the EcoKI methyltransferase.
• Unusual 2-aminopurine fluorescence from a complex of DNA and the EcoKI methyltransferase