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Updated: Aug 30, 2026

Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1
Published on: February 25, 2016
The Drosophila melanogaster UMP-CMP kinase cDNA encodes an N-terminal mitochondrial import signal
Sophie Curbo1, Marjan Amiri, Fariba Foroogh
1Division of Clinical Virology F68, Karolinska Institute, Huddinge University Hospital, S-14186 Stockholm, Sweden. Sophie.Curbo@labmed.ki.se
Abstract:
Drosophila melanogaster cells express a multi-substrate deoxyribonucleoside kinase that phosphorylates both purine and pyrimidine deoxyribonucleosides. The subsequent phosphorylation step is catalyzed by nucleoside monophosphate kinases. We have cloned and characterized the D. melanogaster UMP-CMP kinase (Dm.UMP-CMP kinase) to further study the nucleotide metabolizing enzymes in these cells. The kinase, encoded by the dak1 gene, was approximately 60% similar to the human UMP-CMP kinase and predominantly phosphorylated CMP, dCMP, and UMP. Expression analysis showed that the Dm.UMP-CMP kinase mRNA was constitutively expressed throughout the Drosophila development. The open-reading frame of the Dm.UMP-CMP kinase cDNA was extended in the 5'-region compared to UMP-CMP kinases of other species. The extended region encoded an N-terminal sequence with properties characteristic of a mitochondrial import signal. Expression of the enzyme in fusion with the green fluorescent protein verified that the N-terminal signal targeted the enzyme to mitochondria. This is the first time a mitochondrial pyrimidine nucleoside monophosphate kinase has been cloned from any organism and we discuss the implication of this finding for deoxyribonucleoside salvage in both Drosophila and other organisms.
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