Intraerythrocytic polyubiquitin expression in Plasmodium falciparum is subjected to developmental and heat-shock control.

The polyubiquitin gene of the human protozoan parasite Plasmodium falciparum (PfpUB) was cloned and shown to be comprised of five tandem repeats of the ubiquitin open reading frame, present as a single copy on chromosome 12. The 1672 bp of PfpUB is interrupted at the 5' end by a single intron of 526 bp. PfpUB expression is developmentally regulated in intraerythrocytic stages with a marked increase in both steady-state transcript and polyubiquitin protein levels in late trophozoite stages. On response to heat shock, late stage parasites (late trophozoites and schizonts) have a slightly elevated PfpUB transcript level as well as readily observable increases in the amount of polyubiquitin and ubiquitin-conjugated proteins.