Inhibition of cell growth through inactivation of eukaryotic translation initiation factor 5A (eIF5A) by deoxyspergualin.

The mechanism of inhibition of cell growth by deoxyspergualin was studied using mouse mammary carcinoma FM3A cells. Results of studies using deoxyspergualin analogues showed that both the guanidinoheptanate amide and glyoxyspermidine moieties of deoxyspergualin were necessary to cause inhibition of cell growth. When deoxyspergualin was added to the medium, there was a strong inhibition of cell growth and formation of active eukaryotic translation initiation factor 5A (eIF5A) at the third day of culture. There was also a marked decrease in cellular putrescine content and a small decrease in spermidine content. Accumulation of decapped mRNA, which is typically associated with eIF5A deficiency in yeast, was also observed. The inhibition of cell growth and the formation of active eIF5A was not reversed by addition of spermidine. The activity of deoxyhypusine synthase, the first enzyme in the formation of active eIF5A, was inhibited by deoxyspergualin in a cell-free system. These results, taken together, indicate that inhibition of active eIF5A formation is strongly involved in the inhibition of cell growth by deoxyspergualin.