title: Catalytic DNAzymes: derivations and functions.
abstract: BACKGROUND
  Although catalytic RNA enzymes (CRzs) are naturally occurring in many organisms, their DNA counterparts (CDzs) were developed by in vitro selection/evolution from random sequence libraries.
  
  
  OBJECTIVE
  To provide a brief overview of how CDzs have been selected in vitro, and of their properties and functions, as well as their possible future utility.
  
  
  METHODS
  We concentrated on examples of 'direct' selection of CDzs. Many CDzs have been used in biological settings, for example downregulation of target mRNAs, while many more recent applications use CDzs in biosensor and nanotechnology settings.
  
  
  CONCLUSIONS
  Although much work has concentrated on using CDzs for regulating gene expression, their potential as nucleic acid medicines has diminished substantially, supplanted by simple antisense oligonucleotides and, more recently, by small interfering RNAs (siRNAs). It seems unlikely that CDzs will have clinical utility. In contrast, they are likely to have significant potential in the sensor/nanotechnology arena.
authors.affiliation: Department of Pathology, Pennsylvania State University, Gittlen Cancer Research Foundation, Hershey Medical Center, Hershey, PA 17033, USA.
authors.forename: Weihua
authors.initials: W
authors.lastname: Pan
authors.forename: Gary A
authors.initials: GA
authors.lastname: Clawson
mesh_terms: D001483:Base Sequence; D015374:Biosensing Techniques; D002384:Catalysis; D021881:DNA, Catalytic / Q000737:chemistry / Q000378:metabolism*; D036103:Nanotechnology
chemical_list: D021881:DNA, Catalytic