Page 81 - Academic Press Encyclopedia of Physical Science and Technology 3rd Molecular Biology

P1: GRB/GRD P2: GNB Final Pages Qu: 00, 00, 00, 00
Encyclopedia of Physical Science and Technology EN014F-661 July 28, 2001 20:35

Ribozymes

Alessandra Poggi
John J. Rossi
Beckman Research Institute of the City of Hope

I. Introduction
II. Group I and Group II Introns
III. Ribonuclease P
IV. Self-Cleaving RNAs
V. Ribozymes as Tools and Gene Therapy Agents
VI. Conclusions

GLOSSARY in a group I self-splicing intron of the Tetrahymena pre-
rRNA and in the ribonuclease (RNase) P enzyme purified
Cis The same strand of RNA. from Escherichia coli. Today there are many additions to
Functional genomics Identifying the function of genetic the ribozyme world, including members of the group I and
sequences. II introns, the self-cleaving domains of the genomes of vi-
Gene therapy Supplying therapeutic genes or genetic el- roids, virusoids, hepatitis D, and a Neurospora satellite
ements to treat disease. RNA. It has been proposed that the 23S RNA component
Genotype The genetic makeup of an organism. of the ribosome may function as a ribozyme in transla-
Introns Sequences interrupting the coding sequence of a tion, and the U6 snRNA in the spliceosome. Ribozymes
gene or RNA transcript. occur naturally, but can also be artificially engineered and
Phenotype The result of gene expression. synthesized to target specific sequences in cis or trans.
Ribozymes RNA molecules with enzymatic activities. New biochemical activities are being developed using in
Trans A different strand of RNA. vitro selection protocols as well. Ribozymes can easily
be manipulated to act on novel substrates. These custom-
designed RNAs have great potential as therapeutic agents
I. INTRODUCTION and are becoming a powerful tool for molecular biologists.
The discovery of catalytic RNA molecules has revo-
Ribozymes are RNA molecules capable of acting as en- lutionized views on the origins of life. RNA molecules,
zymes even in the complete absence of proteins. They have once thought to be primarily passive carriers of genetic
the catalytic activity of breaking and/or forming covalent information, can carry out some functions previously only
bonds with extraordinary specificity, accelerating the rate thought to be catalyzed by proteins, indicating that RNA
of those reactions. They were simultaneously discovered can confer not only a genotype (as in many RNA viruses),

253