Identification and characterization of human deoxyguanosine kinase cDNA fragments

Mitochondria require deoxyribonucleoside, triphosphates for the synthesis o f their DNA and one of the enzymes responsible for the initial phosphorylat ion of purine deoxyribonucleoside is deoxyguanosine kinase (dGK; EC 2.7.1.1 13). Recent studies have suggested that dGK in addition to deoxycytidine ki nase phosphorylates several anti-cancer agents, such as 9-beta -D-arabinofu ranosylguanine (Ara-G), cladribine (CdA), and fludarabine. There appear to coexist several mRNA fragments of dGK. In the present study we found 10 fra gments, the longest fragment had 834 bp, and represented the entire open re ading frame of dGK (780 bp). The nine additional fragments detected ranged from 807 to 269 bp. All the fragments were found to contain the specific mi tochondria translocation signal sequence. Expression of these fragments in Escherichia coli demonstrated that only the full-length dGK resulted in a p rotein that could phosphorylate CdA and Ara-G. Given the difficulty to meas ure the full-length dGK, these data are of value for studying the mRNA gene expression of dGK in cell lines and in leukemic cells from patients. (C) 2 001 Elsevier Science Ireland Ltd. All rights reserved.