Stimulates the RNA helicase activity of EIF4A in the translation initiation complex. Binds weakly mRNA. (Microbial infection) Interacts with HHV-1 Vhs. The short isoform is the predominant isoform and is expressed alone in liver and skeletal muscle. Both isoforms are expressed in fibroblast, spleen, testis and bone marrow. Levels are high in lung and pancreas and low in heart, frontal cortex and kidney. EIF4H is located in the Williams-Beuren syndrome (WBS) critical region. WBS results from a hemizygous deletion of several genes on chromosome 7q11.23, thought to arise as a consequence of unequal crossing over between highly homologous low-copy repeat sequences flanking the deleted region. Haploinsufficiency of EIF4H may be the cause of certain cardiovascular and musculo-skeletal abnormalities observed in the disease.