The two genes encoding protein synthesis initiation factor eIF-5A in Saccharomyces cerevisiae are members of a duplicated gene cluster.

Translation initiation factor eIF-5A is an abundant protein in which a lysine residue is modified by spermidine to form the amino acid derivative, hypusine. The factor is encoded by two genes in Saccharomyces cerevisiae, called TIF51A and TIF51B, which are regulated reciprocally by oxygen and by heme. TIF51B, also called ANB1, is located on chromosome X in a region called COR. We physically mapped TIF51A and its associated serine tRNA2 gene by the method of chromosome fragmentation and pulsed-field gel electrophoresis. TIF51A maps 90 kb from the left end of chromosome V in a region called ARC. The COR and ARC regions contain CYC1 and CYC7, respectively, and appear to be duplications carrying numerous related genes. The arrangements of related genes in the two regions are incompatible with a duplication mechanism involving a circular intermediate.