Question

role of initiation factors in translation

Answer 1

Initiation factors are proteins other than the RNA polymerase required for correct initiation of transcription (transcription initiation factors). They are also proteins which, in addition to ribosomal proteins, are required for initiation of translation (translation initiation factors). In eubacteria, transcription initiation factors are called σ factors. In eukaryotes, transcription initiation factors usually refer to the general transcription factors required for transcription initiation from most promoters. For RNA polymerase II these are TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH; for RNA polymerase III these are TFIIIB, as well as TFIIIC, for tRNA genes, and TFIIIA and TFIIIC for 5S rRNA genes; and for RNA polymerase I these are SL1 and UBF in humans, and TBP, Rrn3, core factor, and upstream activating factor in Saccharomyces cerevisiae. Bacterial translation initiation factors are called IF1, IF2, and IF3. Eukaryotic translation initiation factors include eIF1, eIF2, eIF3, eIF4, and eIF5. The eIF4E subunit of eIF4 binds to the 5′ cap structure on eukaryotic mRNAs.
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