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oskar is a gene required for the development of the Drosophila embryo. It defines the posterior pole during early embryogenesis. Its two isoformas, short and long, play different roles in Drosophila embryonic development.

Translational-level regulation[edit]

oskar is translationally repressed prior to reaching the posterior pole of the oocyte by Bruno, which binds to three bruno response elements (BREs) on the 3' end of the transcribed oskar mRNA.[1] The Bruno inhibitor has two distinct modes of action: recruiting the Cup eIF4E binding protein, which is also required for oskar mRNA localization due to interactions with the Barentsz microtubule-linked transporter,[2] and promoting oligomerization of oskar mRNA.[3] Oskar mRNA harbours a stem-loop structure in the 3’UTR, called the oocyte entry signal (OES), that promotes dynein-based mRNA accumulation in the oocyte.[4]


  1. ^ Kim-Ha J, Kerr K, Macdonald PM (1995). "Translational regulation of oskar mRNA by bruno, an ovarian RNA-binding protein, is essential". Cell. 81 (3): 403–12. doi:10.1016/0092-8674(95)90393-3. PMID 7736592. 
  2. ^ Wilhelm JE, Hilton M, Amos Q, Henzel WJ (2003). "Cup is an eIF4e binding protein required for both the translational repression of oskar and the recruitment of Barentsz". JCB. 163 (6): 1197–204. doi:10.1083/jcb.200309088. PMC 2173729Freely accessible. PMID 14691132. 
  3. ^ Chekulaeva M, Hentze MW, Ephrussi A (2006). "Bruno acts as a dual repressor of oskar translation, promoting mRNA oligomerization and formation of silencing particles". Cell. 124 (3): 521–33. doi:10.1016/j.cell.2006.01.031. PMID 16469699. 
  4. ^ Jambore, H. (2014). "A stem-loop structure directs oskar mRNA to microtubule minus ends". RNA. 20: 429–439. doi:10.1261/rna.041566.113. PMC 3964905Freely accessible. PMID 24572808.