Overview: what are helicases?

First discovered in the 1970s, DNA helicases were initially described as enzymes that use chemical energy to separate (i.e., to unwind) the complementary strands of DNA. Because helicases are ubiquitous, display a range of fascinating biochemical activities, and are involved in all aspects of DNA metabolism, defects in human helicases are linked to a variety of genetic disorders, and helicase research continues to be important in understanding the molecular basis of DNA replication, recombination, and repair. The purpose of this book is to organize this information and to update the traditional view of these enzymes, because it is now evident that not all helicases possess bona fide strand separation activity and may function instead as energy-dependent switches or translocases. In this chapter, we will first discuss the biochemical and structural features of DNA-the lattice on which helicases operate-and its cellular organization. We will then provide a historical overview of helicases, starting from their discovery and classification, leading to their structures, mechanisms, and biomedical significance. Finally, we will highlight several key advances and developments in helicase research, and summarize some remaining questions and active areas of investigation. The subsequent chapters will discuss these topics and others in greater detail and are written by experts of these respective fields.