S-trityl-L-cysteine is a reversible, tight binding inhibitor of the human kinesin Eg5 that specifically blocks mitotic progression.

Abstract : Human Eg5, responsible for the formation of the bipolar mitotic spindle, has been identified recently as one of the targets of S-trityl-L-cysteine, a potent tumor growth inhibitor in the NCI 60 tumor cell line screen. Here we show that in cell-based assays S-trityl-L-cysteine does not prevent cell cycle progression at the S or G(2) phases but inhibits both separation of the duplicated centrosomes and bipolar spindle formation, thereby blocking cells specifically in the M phase of the cell cycle with monoastral spindles. Following removal of S-trityl-L-cysteine, mitotically arrested cells exit mitosis normally. In vitro, S-trityl-L-cysteine targets the catalytic domain of Eg5 and inhibits Eg5 basal and microtubule-activated ATPase activity as well as mant-ADP release. S-trityl-L-cysteine is a tight binding inhibitor (estimation of K(i,app) <150 nm at 300 mm NaCl and 600 nm at 25 mm KCl). S-trityl-L-cysteine binds more tightly than monastrol because it has both an approximately 8-fold faster association rate and approximately 4-fold slower release rate (6.1 microM(-1) s(-1) and 3.6 s(-1) for S-trityl-L-cysteine versus 0.78 microM(-1) s(-1) and 15 s(-1) for monastrol). S-trityl-L-cysteine inhibits Eg5-driven microtubule sliding velocity in a reversible fashion with an IC(50) of 500 nm. The S and D-enantiomers of S-tritylcysteine are nearly equally potent, indicating that there is no significant stereospecificity. Among nine different human kinesins tested, S-trityl-L-cysteine is specific for Eg5. The results presented here together with the proven effect on human tumor cell line growth make S-trityl-L-cysteine a very attractive starting point for the development of more potent mitotic inhibitors.
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Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, 2006, 281 (26), pp.17559-69. 〈10.1074/jbc.M511735200〉
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Dimitrios Skoufias, Salvatore Debonis, Yasmina Saoudi, Luc Lebeau, Isabelle Crevel, et al.. S-trityl-L-cysteine is a reversible, tight binding inhibitor of the human kinesin Eg5 that specifically blocks mitotic progression.. Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, 2006, 281 (26), pp.17559-69. 〈10.1074/jbc.M511735200〉. 〈inserm-00380097〉

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