Figure 4.

Model for Processome Assembly and the Maturation of Pre-40S Particles in Arabidopsis.

The picture illustrates UtpA (green), UtpB (blue), UtpC (yellow), U3 snoRNP (violet), Dbp4/Enp2/Brf2 (pink), and Mpp10/Imp3/Imp4 (brown) subcomplexes. Arabidopsis homologs (NuGWD1/Utp5, Nucleolin/Nrs1, Utp25, THAL1/Utp3, RH57/Rock1, RH10/Rrp3, and SW3/Dbp8) or specific (PCP1/2) factors that interact with processome factors or subunits are represented in dark blue. Arabidopsis homologs that interact with the processome and are required for pre-40S maturation and transport are represented in red. Known or predicted Arabidopsis homologs are labeled in white and those not yet identified in black. The anticipated assembly of pre-60S particles on nascent pre-RNA is shown. Assembly might initiate on full-length rRNA precursor or after cleavage at A₂/A₃ sites that release processome factor precursors and pre-40S particles. The figure was adapted and drawn from models of the assembly steps of the 90S/SSU-processome and pre-40S in yeast and mammalian cells (Soltanieh et al., 2014; Cerezo et al., 2019). Accession numbers for all the Arabidopsis factors are provided in Supplemental Data Set 2.