The processes of DNA replication, recombination, transcription, and chromatin remodeling are accompanied by the formation of complex macromolecular assemblies of proteins and nucleic acids. A wealth of experimental information has been obtained about the structure and interaction of individual components of such assemblies (by X-ray crystallography, NMR, FRET, footprinting, and suppression analyses, etc.) but the mechanical properties and formation energies of the assemblies, which strongly affect their biological functions, are not known. Recently developed mesoscale theory of sequence-dependent DNA elasticity and methods for calculating configuration of DNA segments subject to imposed constraints make it possible to create structural models of such assemblies and study their deformability. The talk will focus on applications to two nucleo-protein complexes which play an important role in the regulation of transcription of the lacZ gene in E. coli: the LacR-DNA promoter complex and the CAP-dependent transcription-activation complex. In both cases the structural and mechanical models yielded new information about the mechanism of gene control and the role of promoter sequence in that mechanism.
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