| 摘要 |
The present invention relates to cells and cell strains that are resistant to the killing effects of one or more toxic genes, particularly those that kill hosts in the absence of a suppressing function, e.g. kicB or ccdB. The host cells may comprise one or more suppression mutations, such as deletional or insertional mutations in gyrA, endA or recA, or combinations thereof (particularly gyrA/endA or gyrA/recA), which allow cell strains carrying the one or more suppression mutations to survive the presence and/or expression of one or more toxic genes within their genome or in extrachromosomal genetic elements within the host cell. Preferred host cell strains include prokaryotic host cells, particularly specified strains of E. coli containing the gyrA462 mutation and/or one or more additional mutations, such as DB3, DB3.1, DB4 and DB5. The host cells of the invention are useful in producing recombinant genetic constructs, particularly cDNAs and cDNA libraries, via traditional genetic engineering techniques or via recombinational cloning using engineered recombination sites. The host cells are also useful in cloning and propagation of toxic genes that act upon DNA gyrase, such as ccdB.
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