The efficiency of gene targeting by integration
through homologous recombination (homologous integration,
HI) in the human pathogen Cryptococcus neoformans
remains unsatisfactory. In order to achieve a much more
efficient gene targeting system in C. neoformans, a new
double knockout strain in genes involved in the nonhomologous
end joining (NHEJ) pathway was constructed.
HI frequency was elevated by as much as approximately
fivefold in the single or double knockout strains in NHEJ
genes, and the frequency depended on the gene targeted.
None of the NHEJ gene knockouts showed significant
differences in regular growth, sensitivity to DNA-damaging
drugs or UV, and virulence compared to the wild-type
control, suggesting that the NHEJ pathway does not play a
significant role in these biological stresses in C. neoformans.
It was also suggested that the genes analyzed in this
study are components of a single NHEJ pathway, as the
mutants (including the double mutant) displayed the same
phenotypes.