Co-existence of circular and multiple linear amplicons in methotrexate-resistant Leishmania.
AUTOR(ES)
Olmo, A
RESUMO
Circular and linear amplicons were analyzed in detail in Leishmania tropica cells resistant to methotrexate (MTX). Both types of elements presented sequences related to the H locus and coexisted in resistant cells. The linear amplicons appeared first during the selection process (at 10 microM MTX) and varied with regard to size and structure in cells exposed to increasing concentrations of drug. The circular element was evident at higher concentrations (50 microMs) but was the major amplified DNA in cells resistant to 1000 microM MTX while the level of amplification of the linear elements remained low. The extrachromosomal DNAs were unstable in the absence of drug and their disappearance coincided with an increase in sensitivity to MTX. Mapping of the minichromosomes and the circular element showed that they were all constituted by inverted duplications. The circular amplicon contained an inverted repeat derived from the H locus that encompassed the pteridine reductase gene (PTR1) responsible for MTX resistance. The amplified segment in the linear amplicons was longer and included the pgpB and pgpC genes that encode P-glycoproteins of unknown function previously characterized in different Leishmania species.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=307122Documentos Relacionados
- Linear amplicons as precursors of amplified circles in methotrexate-resistant Leishmania tarentolae.
- Frequent amplification of a short chain dehydrogenase gene as part of circular and linear amplicons in methotrexate resistant Leishmania.
- Multiple origins of replication in the dihydrofolate reductase amplicons of a methotrexate-resistant chinese hamster cell line.
- Organization and genesis of dihydrofolate reductase amplicons in the genome of a methotrexate-resistant Chinese hamster ovary cell line.
- Overproduction of a bifunctional thymidylate synthetase-dihydrofolate reductase and DNA amplification in methotrexate-resistant Leishmania tropica.