title: The eIF3c/NIP1 PCI domain interacts with RNA and RACK1/ASC1 and promotes assembly of translation preinitiation complexes.
abstract: Several subunits of the multifunctional eukaryotic translation initiation factor 3 (eIF3) contain well-defined domains. Among them is the conserved bipartite PCI domain, typically serving as the principal scaffold for multisubunit 26S proteasome lid, CSN and eIF3 complexes, which constitutes most of the C-terminal region of the c/NIP1 subunit. Interestingly, the c/NIP1-PCI domain is exceptional in that its deletion, despite being lethal, does not affect eIF3 integrity. Here, we show that a short C-terminal truncation and two clustered mutations directly disturbing the PCI domain produce lethal or slow growth phenotypes and significantly reduce amounts of 40S-bound eIF3 and eIF5 in vivo. The extreme C-terminus directly interacts with blades 1-3 of the small ribosomal protein RACK1/ASC1, which is a part of the 40S head, and, consistently, deletion of the ASC1 coding region likewise affects eIF3 association with ribosomes. The PCI domain per se shows strong but unspecific binding to RNA, for the first time implicating this typical protein-protein binding domain in mediating protein-RNA interactions also. Importantly, as our clustered mutations severely reduce RNA binding, we conclude that the c/NIP1 C-terminal region forms an important intermolecular bridge between eIF3 and the 40S head region by contacting RACK1/ASC1 and most probably 18S rRNA.
authors: Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, the Czech Republic.
authors: Tomáš
authors: T
authors: Kouba
authors: Edit
authors: E
authors: Rutkai
authors: Martina
authors: M
authors: Karásková
authors: Leoš  Shivaya
authors: L
authors: Valášek
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D039621:Eukaryotic Initiation Factor-3 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010442:Peptide Chain Initiation, Translational; D054730:Protein Interaction Domains and Motifs; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012337:RNA, Ribosomal, 18S / Q000378:metabolism*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C111825:ASC1 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D050976:Basic-Leucine Zipper Transcription Factors; D039621:Eukaryotic Initiation Factor-3; C501391:GCN4 protein, S cerevisiae; C077915:NIP1 protein, S cerevisiae; D021122:Protein Subunits; D012337:RNA, Ribosomal, 18S; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins