Cell-free coupled transcription-translation system for investigation of linear DNA segments.

Abstract
Heretofore the DNA-directed coupled transcription-translation system, most useful in gene expression analysis, was limited to the use of circular or long linear DNA. Linear DNA are degraded in this system by an exonucleolytic activity that can be eliminated by making the synthetic extracts from a suitable recB mutant of Escherichia coli. Use of these extracts permitted examination of the gene expression of a variety of linear DNA. In particular, the complex pattern of expression of ribosomal protein genes and RNA polymerase genes in the rpoBC-rplLJ region was analyzed by comparing the protein products obtained when using .lambda. rifd 18 DNA with the product obtained when using the same DNA segmented with various restriction enzymes. The results obtained confirm the conclusions of others obtained by much more elaborate in vivo techniques. It seems highly likely that this cell-free system will have extensive applications in the area of analysis of gene expression.