Eukaryotic translation initiation factor 4H, also known as EIF4H, is a 248aa protein that localizes to the perinuclear region of the cytoplasm and is expressed as two isoforms, designated short and long. EIF4H induces the RNA-dependent ATP hydrolysis catalyzed by the initiation factors EIF4A and EIF4B. EIF4H was further shown to stimulate the initial rate and extent of EIF4A-mediated mRNA secondary structure unwinding. Defects in the gene encoding EIF4H are associated with Williams- Beuren syndrome (WBS), a rare developmental disorder characterized by cardiovascular and musculo-skeletal abnormalities.