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Translational control mediates the developmental regulation of the Trypanosoma brucei Nrk protein kinase.
Title | Translational control mediates the developmental regulation of the Trypanosoma brucei Nrk protein kinase. |
Publication Type | Journal Article |
Year of Publication | 1994 |
Authors | Gale, M, Carter, V, Parsons, M |
Journal | J Biol Chem |
Volume | 269 |
Issue | 50 |
Pagination | 31659-65 |
Date Published | 1994 Dec 16 |
ISSN | 0021-9258 |
Keywords | Animals, Base Sequence, Blotting, Western, DNA Primers, Gene Expression Regulation, Developmental, Genes, Protozoan, Intracellular Signaling Peptides and Proteins, Molecular Sequence Data, Protein Biosynthesis, Protein-Serine-Threonine Kinases, Protozoan Proteins, RNA, Messenger, Substrate Specificity, Trypanosoma brucei brucei |
Abstract | The expression and function of eukaryotic protein kinases is highly regulated, primarily through transcriptional and post-translational processes. In this report we demonstrate an unusual mechanism for controlling protein kinase function, translational control. The Trypanosoma brucei Nrk loci encode predicted protein kinases. Here we show that Nrk has protein serine-threonine kinase activity and examine the expression and activity of Nrk during parasite development. While Nrk transcripts were previously found to be constitutively expressed throughout the life cycle, we now find that expression of Nrk protein is highly stage-regulated. Immunoblot analysis revealed that Nrk expression dramatically increased as the parasites differentiated from proliferative slender bloodforms to the non-proliferative stumpy bloodforms. Procyclic form organisms expressed moderate levels of Nrk. Analysis of Nrk activity demonstrated that it too was highest in stumpy bloodforms. Metabolic labeling and pulse-chase analysis demonstrated that Nrk accumulation was highest in stumpy bloodforms and indicated that Nrk abundance is primarily controlled at the level of biosynthesis rather than turnover. All Nrk mRNA was contained in the poly(A)+ fraction, and the 5' ends of the transcript were the same in each developmental stage. Thus, Nrk is under translational control. The strict developmental regulation of the Nrk enzymes within the trypanosome life cycle suggests that the Nrk protein kinase may play a role in parasite differentiation. |
Alternate Journal | J. Biol. Chem. |
PubMed ID | 7989338 |