The Effects of EIF5A and of the Polyamines on RNA Processing, Translation, and P-Body Formation

The polyamines positively charged molecules that are able to affect nucleic acid structure. Investigation of polyamine and RNA interaction shows that the two are able to form aggregates and these aggregates may be responsible for the inhibition of RNA decapping that is seen in the presence of polyamines. The polyamines are also responsible for a post-translational modification of a protein, eukaryotic initiation factor 5a (eIF5A). This protein is known to affect translation and RNA decay. This investigation shows that eIF5A is able to affect the formation of foci by Dhh1 but does not affect DCP1 or DCP2 foci formation. This investigation also shows that eIF5A mutation leads to a depression of polysome profiles and 35S-met incorporation and therefore eIF5A may truly be a translation initiation factor. This study also describes unique interactions of eIF5A with Dhh1p and eIF5A-independent effects of the polyamines on gene expression. The inhibition of eIF5A's hypusine modification leads to an increase in phoshorylation of eIF2α and this may contribute the induction of apoptosis and inhibition of protein synthesis associated with inhibition of eIF5A's hypusine modification