ABSTRACT
Proteins interacting with nucleic acids are considered particularly important because they control some of the most fundamental biological processes, including replication, recombination, DNA repair, transcription, RNA processing and protein synthesis. Protein-nucleic acid interactions fulfill many roles in the cell, but these can be divided into four major categories: (i) structural and packaging roles (e.g. histones in chromatin, HU in the bacterial nucleoid, viral capsid proteins); (ii) transport and localization roles, including DNA segregation and localization in the nucleus, RNA export and localization, and plasmid transfer; (iii) metabolism and rearrangement roles (e.g. DNA and RNA polymerases, nucleases, helicases, DNA repair enzymes, recombinases, topoisomerases); and (iv) gene expression roles (e.g. RNA polymerases, transcription factors, ribosomes and initiation factors, the RNA splicing apparatus, amino acyl-tRNA synthetases). Many of these functions overlap (e.g. histones are packaging proteins which influence gene expression, RNA polymerases facilitate gene expression but are involved in RNA metabolism). All nucleic acids are associated with proteins at some time during their life, and many exist as permanent nucleoprotein complexes.
