Function: mRNA-binding protein involved in translation elongation. Has an important function at the level of mRNA turnover, probably acting downstream of decapping. Involved in actin dynamics and cell cycle progression, mRNA decay and probably in a pathway involved in stress response and maintenance of cell wall integrity. Functions as a regulator of apoptosis. Mediates effects of polyamines on neuronal process extension and survival. May play an important role in brain development and function, and in skeletal muscle stem cell differentiation. Tissue specificity: Expressed in ovarian and colorectal cancer cell lines (at protein level). Highly expressed in testis. Overexpressed in some cancer cells. Similarity: Belongs to the eIF-5A family. PTM: eIF-5A seems to be the only eukaryotic protein to have an hypusine residue which is a post-translational modification of a lysine by the addition of a butylamino group (from spermidine).