Multiple DNA-protein interactions governing high-precision DNA transactions.

The precise association of DNA-binding proteins with localized regions of DNA is crucial for regulated replication and expression of the genome. For certain DNA transactions, the requirement for precision in localization and control is extremely high. High-precision events amenable to detailed biochemical analysis are the initiation of DNA replication and site-specific recombination by bacteriophage lambda and Escherichia coli. Recent experiments indicate that site-localization and control in these reactions involves the association of DNA-bound proteins to generate organized nucleoprotein structures in which the DNA is folded or wound. These specialized nucleoprotein structures are likely to provide the requisite accuracy for site localization and the necessary regulated reactivity to direct the DNA transaction. Multiple DNA-protein interactions are also required for controlled transcription of the eukaryotic genome. Distant upstream regulator and enhancer sequences may define protein-binding sites that form part of a reactive nucleoprotein structure capable of initiating transcription.