Photosensitized Cross-Linking of Proteins to Nucleic Acids

Abstract

Cross-linking of nucleic acids and proteins represents one of the many reactions that can take place when bacteria or mammalian cells are irradiated with UV light. Every cell contains a lot of potential photosensitizer molecules whose excitation in a wavelength region where neither proteins nor nucleic acids absorb light might lead to the formation of cross-links between these two macromolecules. One might contemplate applying methods similar to those developed for the selective modification of nucleic acids, e.g., acetophenone photosensitization produces practically only cyclobutane-type thymine dimers in DNA (Lamola, 1972). If it appeared possible to create a well-defined chemical link between a particular amino acid side chain and a nucleic acid base, then the method might become an important and specific tool in the investigation of protein-nucleic acid complexes. The applicability of the method to provide evidence for the close proximity of protein and nucleic acid species in multimacromolecular systems such as ribosomes, chromatin, etc..., might also help in understanding the architecture of these systems. The potentialities of the photosensitization method are therefore very diverse. In the present report photosensitized reactions leading to nucleic acid-protein cross-linking are reviewed.