Figure 6. Translational control by proteins associated with the eIF4 cap-binding complex.

CBE1 is an eIF4E binding protein that is phosphorylated in a TOR-dependent manner (Patrick et al., 2018). CERES likewise forms cap-binding complexes with eIF4E/iso4E, which lack eIF4G/iso4G (Toribio et al., 2019).

Activity of the RNA helicase eIF4A is stimulated by MRF proteins, likely through phosphorylation through the TOR kinase pathway (based on Lee et al., 2017). In contrast, phosphorylation of eIF4A by cyclin-dependent kinase may inhibit eIF4A (after Hutchins et al., 2004 and Bush et al., 2016). The RNA binding protein SOAR1 inhibits translation initiation, likely by disrupting the interaction between eIF4G and poly(A) binding proteins. SOAR1 can also bind directly to mRNAs such as the one for ABI5, an abscisic acid-signaling transcription factor (after Mei et al., 2014 and Bi et al., 2019). The jasmonic acid inducible protein JIP60 in barley undergoes proteolytic cleavage upon methyl-jasmonate (MeJA) treatment, which liberates a domain resembling ribosome inactivating protein (RIP30) and an eIF4E-like domain. Uncleaved JIP60 also induces the dissociation of the 80S subunit by an unknown mechanism (after Rustgi et al., 2014). MRF: MA3-containing translation regulatory factor; CDKA: Cyclin-dependent kinase A; eIF: Eukaryotic initiation factor; SOAR1: Suppressor of the ABA Receptor-overexpressor 1; JIP: Jasmonate-induced protein; RIP: Ribosome inactivating protein. Some of the findings presented in this figure are correlative or based on circumstantial evidence.