Mutations at serine 37 in mouse guanylate kinase confer resistance to 6-thioguanine.
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| Abstract |
Guanylate kinase (GMK) is an essential nucleoside monophosphate kinase that catalyzes the phosphorylation of guanine-monophosphate (GMP) and dGMP to yield GDP and dGDP, respectively, important precursors for nucleotide synthesis. GMK is also responsible for the activation of 6-thioguanine (6-TG), a drug widely used as chemotherapeutic agent to treat leukemia. Several mechanisms of resistance to 6-TG have been reported but a subset of drug resistant cells cannot be explained by these mechanisms. We propose that mutations in GMK could result in drug resistance. Because cells require the presence of a functional GMK for viability, mutations that arise that lead to 6-TG resistance must retain activity toward GMP. We report three amino acid substitutions at serine 37 (S37) in mouse GMK that display activity toward GMP by conferring genetic complementation to a conditional GMK-deficient Escherichia coli and in enzyme assays. When 6-TG is included in complementation studies, cells expressing wild-type GMK are sensitive whereas all S37 mutants examined are able to effectively discriminate against 6-TG and display a drug resistance phenotype. Activity of the three S37 mutant enzymes toward clinically relevant concentrations of 6-TGMP is undetectable. Mutations in GMK, therefore, represent a previously undescribed mechanism for 6-TG resistance.
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| Authors | Andressa Ardiani, Amanda Goyke, Margaret E Black |
| Journal | Protein engineering, design & selection : PEDS (Protein Eng Des Sel) Vol. 22 Issue 4 Pg. 225-32 (Apr 2009) ISSN: 1741-0134 [Electronic] England |
| PMID | 19136674 (Publication Type: Journal Article, Research Support, N.I.H., Extramural) |
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