MOLECULAR-CLONING AND FUNCTIONAL EXPRESSION OF A HUMAN CDNA-ENCODING TRANSLATION INITIATION-FACTOR-6

Eukaryotic translation initiation factor 6 (eIF6) binds to the 60S rib osomal subunit and prevents its association with the 40S ribosomal sub unit. In this paper, we devised a procedure for purifying eIF6 from ra bbit reticulocyte lysates and immunochemically characterized the prote in by using antibodies isolated from egg yolks of laying hens immunize d with rabbit eIF6. By using these monospecific antibodies, a 1.096-kb human cDNA that encodes an eIF6 of 245 amino acids (calculated M-r 26 ,558) has been cloned and expressed in Escherichia coli. The purified recombinant human protein exhibits biochemical properties that are sim ilar to eIF6 isolated from mammalian cell extracts. Database searches identified amino acid sequences from Saccharomyces cerevisiae, Drosoph ila, and the nematode Caenorhabditis elegans with significant identity to the deduced amino acid sequence of human eIF6, suggesting the pres ence of homologues of human eIF6 in these organisms.