Genomic organization and gene function in Leishmania

Sequencing of the Leishmania major Friedlin genome is well underway with ch romosome 1 (Chr1) and Chr3 having been completely sequenced, and Chr4 virtu ally complete. Sequencing of several other chromosomes is in progress and t he complete genome sequence may be available as soon as 2003. A large propo rtion (approximate to 70%) of the newly identified genes remains unclassifi ed, with many of these being potentially Leishmania- (or kinetoplastid-) sp ecific. Most interestingly, the genes are organized into large (> 100-300 k b) polycistronic clusters of adjacent genes on the same DNA strand. Chr1 co ntains two such clusters organized in a 'divergent' manner, i.e. the mRNAs for the two sets of genes are both transcribed towards the telomeres. Chr3 contains two 'convergent' clusters, with a single 'divergent' gene at one t elomere, with the two large clusters separated by a tRNA gene. We have char acterized several genes from the LD1 (Leishmania DNA 1) region of Chr35. BT 1 (formerly ORFG) encodes a biopterin transporter and ORFF encodes a nuclea r protein of unknown function. Immunization of mice with recombinant antige ns from these genes results in significant reduction in parasite burden fol lowing Leishmania challenge. Recombinant ORFF antigen shows promise as a se rodiagnostic. We have also developed a tetracycline-regulated promoter syst em, which allows us to modulate gene expression in Leishmania.