Two functionally redundant isoforms of Drosophila melanogaster eukaryotic initiation factor 4B are involved in cap-dependent translation, cell survival, and proliferation.
Eukaryotic initiation factor (eIF) 4B is part of the protein complex involved in the recognition and binding of mRNA to the ribosome. DrosophilaeIF4B 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 bind RNA with the same affinity. eIF4B-L and eIF4B-S preferentially enhance cap-dependent over IRES-dependent translation initiation in a Drosophila cell-free 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.
Hernández
Greco
G
Max-Planck-Institute für biophysikalische Chemie, Göttingen, Germany.
Vázquez-Pianzola
Paula
P
Zurbriggen
Andreas
A
Altmann
Michael
M
Sierra
José M
JM
Rivera-Pomar
Rolando
R
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D002455:Cell Division / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D039642:Eukaryotic Initiation Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D005816:Genetic Complementation Test; D006801:Humans; D008969:Molecular Sequence Data; D017956:Photoreceptor Cells, Invertebrate / Q000196:embryology / Q000378:metabolism / Q000648:ultrastructure; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D012315:RNA Caps; D034622:RNA Interference; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
D029721:Drosophila Proteins; D039642:Eukaryotic Initiation Factors; D020033:Protein Isoforms; D012315:RNA Caps; D011994:Recombinant Proteins; C031799:eIF-4B