Furthermore, many eIF4GI isoforms have been detected in HeLa cells and these are synthesized from several distinct mRNAs via alternative promoter usage and alternative splicing [105] . The largest is the eIF4GI-a isoform, which contains 1,600 residues, while the eIF4GI-b, -c, -d, ande are shorter variants [106] . It has been described that the longer isoforms are more active in translation initiation, most probably because they contain the PABP-binding site [107] .