Puromycin

Puromycin is an antibiotic protein synthesis inhibitor. 
It causes premature chain termination during translation in the ribosome. Puromycin is used in cell biology as a selective agent in cell culture systems. It is toxic to prokaryotic and eukaryotic cells.
Puromycin is an example of a eukaryotic selection compound. These are compounds which are used in biological research to select for cells/organisms that carry the appropriate resistance gene for the compound.