Nucleic Acids Research, Vol 26, Issue 14 3372-3378, Copyright © 1998 by Oxford University Press
K Grondin, C Kundig, G Roy and M Ouellette
Gene amplification is frequently observed in Leishmania cells selected for
drug resistance. By gene targeting we have tagged both alleles of the H
locus of Leishmania tarentolae with the neomycin and hygromycin
phosphotransferase genes ( neo and hyg ). Selection of these recombinant
parasites for low level methotrexate resistance led to amplification of the
H locus as part of linear amplicons. The availability of tags has permitted
us to determine that both alleles can be amplified in the same cell and
that chromosomal deletions are frequent. When methotrexate concentration
was increased in subsequent selection steps, circles were observed in
several mutants. We have introduced a hyg marker into linear amplicons to
test whether the circles originated from linear amplicons. After selection
with a high methotrexate concentration, circles with the hyg marker were
observed, showing that circles can indeed be formed from linear amplicons.
The tagging of H locus alleles permits appreciation of the extent of
genetic rearrangements leading to amplicon formation in Leishmania cells
selected for drug resistance.
ARTICLES
Linear amplicons as precursors of amplified circles in methotrexate- resistant Leishmania tarentolae
Centre de Recherche en Infectiologie du CHUL and Departement de Biologie Medicale, Division de Microbiologie, Faculte de Medecine, Universite Laval, Quebec, Canada.
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