The Many Faces of Hypusinated eIF5A: Cell Context-Specific Effects of the Hypusine Circuit and Implications for Human Health.

The unique amino acid hypusine [N ^ε -(4-amino-2-hydroxybutyl)lysine] is exclusively formed on the translational regulator eukaryotic initiation factor 5A (eIF5A) via a process coined hypusination. Hypusination is mediated by two enzymes, deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase (DOHH), and hypusinated eIF5A (eIF5A ^Hyp ) promotes translation elongation by alleviating ribosome pauses at amino acid motifs that cause structural constraints, and it also facilitates translation initiation and termination. Accordingly, eIF5A ^Hyp has diverse biological functions that rely on translational control of its targets. Homozygous deletion of Eif5a , Dhps , or Dohh in mice leads to embryonic lethality, and heterozygous germline variants in EIF5A and biallelic variants in DHPS and DOHH are associated with rare inherited neurodevelopmental disorders, underscoring the importance of the hypusine circuit for embryonic and neuronal development. Given the pleiotropic effects of eIF5A ^Hyp , a detailed understanding of the cell context-specific intrinsic roles of eIF5A ^Hyp and of the chronic versus acute effects of eIF5A ^Hyp inhibition is necessary to develop future strategies for eIF5A ^Hyp -targeted therapy to treat various human health problems. Here, we review the most recent studies documenting the intrinsic roles of eIF5A ^Hyp in different tissues/cell types under normal or pathophysiological conditions and discuss these unique aspects of eIF5A ^Hyp -dependent translational control.