tailieunhanh - Báo cáo khoa học: Dimerization of the yeast eukaryotic translation initiation factor 5A requires hypusine and is RNA dependent

Post-translational modification of the highly conserved K51 residue of the Saccharomyces cerevisiae eukaryotic translation initiation factor 5A (eIF5A) to form hypusine, is essential for its many functions including the binding of specific mRNAs. | ỊFEBS Journal Dimerization of the yeast eukaryotic translation initiation factor 5A requires hypusine and is RNA dependent Petra M. Gentz1 Gregory L. Blatch1 2 and Rosemary A. Dorrington1 2 1 Department of Biochemistry Microbiology and Biotechnology Rhodes University Grahamstown South Africa 2 Centre for Chemico- and BiomedicinalResearch Rhodes University Grahamstown South Africa Keywords eIF5A homodimer hypusine RNA binding yeast Correspondence R. A. Dorrington Department of Biochemistry Microbiology and Biotechnology PO Box 94 Rhodes University Grahamstown 6140 South Africa Fax 27 46 622 3984 Tel 27 46 603 8442 E-mail Received 24 September 2008 revised 5 November 2008 accepted 24 November 2008 doi Post-translational modification of the highly conserved K51 residue of the Saccharomyces cerevisiae eukaryotic translation initiation factor 5A eIF5A to form hypusine is essential for its many functions including the binding of specific mRNAs. We characterized hypusinated yeast eIF5A by size-exclusion chromatography and native PAGE showing that the protein exists as a homodimer. A K51R mutant which was not functional in vivo eluted as a monomer and inhibition of hypusination abolished dimerization. Furthermore treatment of dimeric eIF5A with RNase A resulted in disruption of the dimer leading us to conclude that RNA binding is also required for dimerization of eIF5A. We present a model of dimerization based on the Neurospora crassa structural analogue HEX-1. Eukaryotic translation initiation factor 5A eIF5A is found in all eukaryotes and archaebacteria and is unique in that it is the only protein known to undergo a two-step post-translational modification of a highly conserved lysine residue to form hypusine 1 2 . First a spermidine moiety is conjugated to the epsilon amino group of the lysine catalysed by deoxyhypusine synthase DHS followed by hydroxylation by deoxyhupusine hydroxylase to produce hypusine Hpu 3 . .