Mo. Rojas et M. Wasserman, STAGE-SPECIFIC EXPRESSION OF THE CALMODULIN GENE IN PLASMODIUM-FALCIPARUM, Journal of Biochemistry, 118(6), 1995, pp. 1118-1123
We studied the synthesis of calmodulin mRNA and of calmodulin during t
he asexual cell cycle of Plasmodium falciparum. The expression of the
gene was low during the early stages of the erythrocytic asexual cycle
. When the parasites were 28 h old the level of mRNA increased steadil
y to reach a peak at the age of 40 h. During the last 8 h of the cycle
a constant decrease in the amount of calmodulin mRNA was observed. Th
e synthesis of the protein followed the expression pattern of the mRNA
, but without the final decrease, The average amounts of calmodulin me
asured were 2.5+/-0.9 ng/10(8) 14-h-old rings, 4.38+/-0.35 ng/10(8) 36
-h-old trophozoites, 11.8+/-1.45 ng/10(8) 44-h-old trophozoites, and 1
9.6+/-1.9 ng/10(8) 48-h-old schizonts. The in vivo stability of mRNA i
n different developmental stages was evaluated by pulse and chase expe
riments. The RNA of very mature trophozoites was quickly degraded, in
contrast with the high stability shown by the RNA in other stages, The
results here suggest that the calmodulin gene expression in Plasmodiu
m does not follow a housekeeping pattern of expression such as in othe
r eukaryotic cells, but that it is regulated at the level of transcrip
tion and RNA degradation.