Co-Authors:
Siman-Tov, M.M., Department of Parasitohgy, Hebrew Univ.-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel
Radi, A., Department of Weed Research, Newe Ya'ar Research Center, Haifa, Israel
Shapira, M., Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Jaffe, C.L., Department of Parasitohgy, Hebrew Univ.-Hadassah Medical School, P.O. Box 12272, Jerusalem 91120, Israel
Abstract:
Protein kinases are important in the regulation of cellular processes including growth and differentiation. Using the polymerase chain reaction with oligonucleotide primers derived from conserved regions of cAMP-dependent protein kinases (PKAs), three different DNA fragments were amplified from leishmanial genomic DNA. One fragment was used to isolate a stage specific gene, c-lpk2, from a Leishmania major genomic library. This gene shows high homology to other eukaryotic PKAs, and the open reading frame encodes a 332 amino acid protein with a predicted molecular mass of 38.2 kDa. When aligned with other PKAs the leishmanial enzyme has a unique eight amino acid extension at the carboxy terminus. The c-lpk2 gene is present as a single copy in L. major, L. donovani and L. amazonensis. The 5′-flanking region contains a polypyrimidine rich tract upstream from the predicted ATG start codon. The gene is highly expressed in promastigotes and barely detectable in amastigotes of L. major. Temperature increase was shown to rapidly down-regulate c-lpk2 expression. Transfer of L. amazonensis promastigotes to 35°C resulted in the rapid disappearance of c-lpk2 mRNA (>70% in 1 h), while at 26°C the mRNA was more stable. The strict temperature dependence of mRNA degradation rate suggests that PKA expression is regulated post-transcriptionally.
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