Component of the eukaryotic translation initiation factor 3 (eIF-3) complex, which is involved in protein synthesis of a specialized repertoire of mRNAs and, together with other initiation factors, stimulates binding of mRNA and methionyl-tRNAi to the 40S ribosome. The eIF-3 complex specifically targets and initiates translation of a subset of mRNAs involved in cell proliferation (Potential). Regulates translation initiation of specific 5' mRNAs harboring multiple upstream open reading frames (uORFs) in their 5' leader sequence (e.g. BETA-OHASE 2 and LHY) (PubMed:15548739, PubMed:17439654, PubMed:23524850). Component of the eukaryotic translation initiation factor 3 (eIF-3) complex. Interacts directly with TIF3A1, TIF3B1, TIF3C1, TIF3E1 and TIF3F1 (PubMed:15548739, PubMed:20444226). Associates with the CSN (COP9 signalosome) complex. Binds to CSN1, CSN7 and CSN8 (PubMed:15548739). Interacts with ATPK1 (PubMed:23524850). Mostly expressed in roots and flowers, and, to a lower extent, in leaves, stems and siliques. In response to auxin (NAA), phosphorylated at Ser-178 by ATPK1 and binds to polysomes via TOR signaling. This phosphorylation is repressed by Torin-1. Pleiotropic growth defects throughout development including postembryonic growth retardation, and delayed shoot and root growth, flowering, and senescence. Lethal at 80 percent at the vegetative rosettes stage. Reduced fertility. Compromised translation efficiency of specific 5' mRNA leader sequences. Requires exogenous sugar to transit from seedling to vegetative development, but hypersensitive to elevated levels of exogenous sugars (e.g. sucrose, maltose and glucose). Enhanced sensitivity to abscisic acid (ABA) (PubMed:15548739). Impaired uORF-RNAs polysomal association (PubMed:23524850). Belongs to the eIF-3 subunit H family.