Abstract
Two mechanisms of initiation of protein synthesis are known. The 5' cap-dependent model requires the activity of cap-binding eukaryotic initiation factors (eIF)1-4E and -4F, inducing unwinding of mRNA secondary structures. The internal initiation model is 5' cap-independent and requires a ribosomal entry site formed by higher order structures of the mRNA. It has been proposed that this mechanism does not need eIF-4E and eIF-4F. We prepared bicistronic transcripts on which both mechanisms of initiation occur, allowing the determination of the initiation factor dependence of these two mechanisms simultaneously. The unwinding factors eIF-4A, eIF-4B, and eIF-4F were found to be necessary for 5' cap-dependent initiation as well as for internal initiation. Surprisingly, efficient translation of both cistrons on the bicistronic mRNA required eIF-4E. A model is presented in which assembly of eIF-4E into a functional eIF-4F complex is a prerequisite for both types of initiation.
Original language | English |
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Pages (from-to) | 7269-74 |
Number of pages | 6 |
Journal | Journal of Biological Chemistry |
Volume | 267 |
Issue number | 11 |
Publication status | Published - 15 Apr 1992 |
Keywords
- Bacterial Proteins
- Base Sequence
- Electrophoresis, Polyacrylamide Gel
- Escherichia coli
- Eukaryotic Initiation Factor-4E
- Eukaryotic Initiation Factor-4F
- Genes, Viral
- Molecular Sequence Data
- Mosaic Viruses
- Nucleic Acid Conformation
- Peptide Chain Initiation, Translational
- Peptide Initiation Factors
- Plasmids
- RNA Caps
- RNA, Messenger
- Transcription, Genetic