GLYCOPROTEIN-46 MESSENGER-RNA ABUNDANCE IS POSTTRANSCRIPTIONALLY REGULATED DURING DEVELOPMENT OF LEISHMANIA-CHAGASI PROMASTIGOTES TO AN INFECTIOUS FORM

GP46 is an abundant glycoprotein of 46 kDa on the surface of the proma stigote form of mast Leishmania species. We show that the steady stale level of GP46 mRNA increases >30-fold as Leishmania chagasi promastig otes develop in vitro from a less infections form during logarithmic g rowth to a highly infections form in the stationary phase of cultivati on Nuclear run on experiments demonstrate that this increase in GP46 m RNA abundance is regulated post-transcriptionally. Plasmids containing the 3'-untranslated regions (UTRs) and downstream intergenic regions (IRs) of two differ ent GP46 genes fused immediately downstream of the beta-galactosidase coding region were transfected into L. chagasi, an d beta-galactosidase activity and mRNA levels were examined. The prese nce of the 3'-UTR + IR of one GP46 gene (gp46A) resulted in a steady i ncrease in p-galactosidase activity and mRNA level as the transfected promastigotes developed from logarithmic to stationary phase. This dif ferential effect parallels that of the 3'-UTRs + IRs of a family of ge nes for an unrelated Leishmania surface glycoprotein, GP63. Thus, post -transcriptional regulation of the genes for two different surface gly coproteins of Leishmania occurs via a similar mechanism.