Expression of alpha- and beta-Tubulin Genes during Growth of Trypanosoma cruzi Epimastigotes

The expression of tubulin genes was studied during the growth of epimastigotes of Trypanosoma cruzi. Northern blot analysis showed that there was a decrease in the levels of alpha- and beta-tubulin mRNAs as epimastigotes changed from the logarithmic to the stationary phase. The changes were associated with a similar decrease in the rates of transcription for both of these genes as measured by run-on assays using permeabilized parasites. In contrast to these results, ubiquitin transcription increased slightly. The levels of alpha-tubulin protein per parasite also decreased in stationary compared with logarithmic phase epimastigotes, in close agreement with the decrease in transcription. However, beta-tubulin protein levels did not change significantly. Our results thus indicated that during the growth of epimastigotes, the expression of alpha-tubulin is controlled partially at the transcriptional level. On the other hand, the experiments also suggested that beta-tubulin expression is controlled at a post-transcriptional level.