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Free keywords:
cell survival; Drosophila; eukaryotic initiation factor 4B (eIF4B); proliferation; translation
Abstract:
Eukaryotic initiation factor (eIF) 4B is part of the protein complex involved in the recognition and binding of mRNA to the ribosome. Drosophila eIF4B is a single-copy gene that encodes two isoforms, termed eIF4B-L (52.2 kDa) and eIF4B-S (44.2 kDa), generated as a result of the alternative recognition of two polyadeynlation signals during transcription termination and subsequent alternative splicing of the two pre-mRNAs. Both eIF4B mRNAs and proteins are expressed during the entire embryogenesis and life cycle. The proteins are cytoplasmic with polarized distribution. The two isoforms bindRNAwith the same affinity. eIF4B-L and eIF4B-S preferentially enhance cap-dependent over IRES-dependent translation initiation in a Drosophila cellfree translation system. RNA interference experiments suggest that eIF4B is required for cell survival, although only a modest reduction in rate of protein synthesis is observed. Overexpression of eIF4B in Drosophila cells in culture and in developing eye imaginal discs promotes cell proliferation.
