Ideal gene therapy implies correction of a genetic defect at its site
on the chromosome, which can be done only by homologous recombination.
In prokaryotes, two pathways of homologous recombination are provided
by two types of recombinases: ATP-dependent RecA protein and ATP-inde
pendent renaturase. In eukaryotes, both ATP-dependent and ATP-independ
ent DNA transferases have been found, including enzymes functionally s
imilar to the RecA protein. The specific properties of RecA-like prote
ins suggest their involvement in both pro- and eukaryotic recombinatio
n. Recent studies of eukaryotic mitotic cells indicate their potential
for homologous recombination. However, its realization requires a rea
sonable length of donor DNA and a high level of its homology to the re
cipient DNA. Other possible ways of optimizing gene therapy are discus
sed as well.