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, This phosphosite has also been shown to be affected by the light-to-dark transition [11]. The specific role of phosphorylation at this site is presently unclear and eIF4G possesses multiple phosphorylation sites with contrasting effects. In yeast and mammals, phosphorylation of eIF4G near the C-terminus has been shown to stimulate translation by promoting the formation of the eIF4F complex and subsequent binding of 5? RNA cap (for a review

, Ser 178 is situated in the mRNA-binding region [72] and thus phosphorylation likely impedes formation of the eIF4F complex and thus translation initiation. By contrast, translation stimulation appears to be accompanied by increased phosphorylation of eIF4B2 and eIF3d (Fig. 4)

, Thr 283) is not present in some non-Brassicaceae species. eIFs of the eIF3 group are known to be phosphorylated, including eIF3c

, In Mammals, it has been shown that eIF3d allows translation of specific mRNAs independently of the complex eIF4F [76]. It is currently unknown if such a mechanism also takes place in plants (and Arabidopsis eIF3d possesses only 42% identity with human eIF3d)

, ? Possible involvement of SnRK1

, Arabidopsis SnRK1 has been found to be inhibited by a variety of sugar phosphates

, That is, it is plausible that the effect on translation seen here was the combined effect of SnRK1 inhibition when gross photosynthesis increases (increased production of sugars) and photorespiration decreases (lower H2O2 production in photorespiratory cycle). That said, while this mechanism provides a probable explanation for RPS6, it cannot be at the origin of eIFs phosphorylation changes with photosynthesis, fact

, suggesting an important role of these kinases. In particular, CK2-mediated phosphorylation of several plant eIFs has been found to take place

, However, mechanisms regulating CK2 activity are presently unclear. It is generally believed that plant CK2 is a housekeeping

, the ?/? isoform composition of which changes in response to environmental conditions -typically with mineral nutrition

, Also, both phosphorylation and N-acetyl glucosamination of CK2 have been found