Polymerize it all! A critical review

Introduction Polymerases are fascinating and ubiquitous enzymes that catalyse the synthesis of nucleic acids with impressive rates and fidelity. Indeed, polymerases are capable of distinguishing minute differences in nucleoside triphosphates (e.g. the 2'OH residue that is absent in dNTPs but present in rNTPs) and process with very low error rates (~106 for Pfu DNA polymerase, e.g.). However, this stringency is rather detrimental for practical applications since thermal stability (PCR), broad substrate tolerance (in vitro selections, functional tagging, etc.), or absence of exonuclease activity (sequencing) are desirable properties that are governed by the inherent nature of the polymerase. It is thus not surprising that polymerases are the targets of numerous engineering and modification strategies. This review highlights some of the recent progresses made in this field, with a particular emphasis on the substrate tolerance and processivity of mutant polymerases. Conclusion The development of new methods such as compartmentalized selfreplication (CSR) selections and strategies for the screening of larger populations, has led to the generation of polymerases with tailor-made properties, capable of accepting a very broad range of substrates.