The translation initiation factor eIF-4B contains an RNA-binding region that is distinct and independent from its ribonucleoprotein consensus sequence.

Abstract

eIF-4B is a eukaryotic translation initiation factor that is required for the binding of ribosomes to mRNAs and the stimulation of the helicase activity of eIF-4A. It is an RNA-binding protein that contains a ribonucleoprotein consensus sequence (RNP-CS)/RNA recognition motif (RRM). We examined the effects of deletions and point mutations on the ability of eIF-4B to bind a random RNA, to cooperate with eIF-4A in RNA binding, and to enhance the helicase activity of eIF-4A. We report here that the RNP-CS/RRM alone is not sufficient for eIF-4B binding to RNA and that an RNA-binding region, located between amino acids 367 and 423, is the major contributor to RNA binding. Deletions which remove this region abolish the ability of eIF-4B to cooperate with eIF-4A in RNA binding and the ability to stimulate the helicase activity of eIF-4A. Point mutations in the RNP-CS/RRM had no effect on the ability of eIF-4B to cooperate with eIF-4A in RNA binding but significantly reduced the stimulation of eIF-4A helicase activity. Our results indicate that the carboxyterminal RNA-binding region of eIF-4B is essential for eIF-4B function and is distinct from the RNP-CS/RRM.

Angiotensin II Stimulates Phosphorylation of the Translational Repressor 4E-binding Protein 1 by a Mitogen-activated Protein Kinase-independent Mechanism

“…Preparation of Recombinant Proteins-The recombinant GST-4E-BP1 protein was expressed in Escherichia coli and purified as described (29). Plasmid pGST-ERK1 was created by subcloning the EcoRI fragment encoding hamster ERK1 from plasmid pCMV/HAPMK (30) into the EcoRI site of pGEX-KG (31).…”

“…4E-BP1 is phosphorylated by ERK2 on a single serine residue in vitro (23), and this phosphorylation markedly decreases the affinity of the protein for eIF4E (22). In cultured adipocytes, the epidermal growth factor-stimulated 4E-BP1 kinase activity elutes in two peaks that correspond to the peaks of ERK isoforms after anion exchange chromatography (29). Based on these observations, it has been proposed that MAP kinases mediate growth factor-stimulated phosphorylation of 4E-BP1 in intact cells (22).…”

Phosphorylation of Eukaryotic Translation Initiation Factor 4B (EIF4B) by Open Reading Frame 45/p90 Ribosomal S6 Kinase (ORF45/RSK) Signaling Axis Facilitates Protein Translation during Kaposi Sarcoma-associated Herpesvirus (KSHV) Lytic Replication

“…Protein translation is primarily regulated at the step of initiation at which the small ribosome subunit is recruited to the 5Ј-end of mRNA and scans toward the start codon where the initiation complex joins the large subunit to form a complete ribosome (80 S) and begin polypeptide formation (1)(2)(3)(4). Many eukaryotic translation initiation factors (eIFs) are involved in the initiation process.…”

“…eIF4B is an avid RNA-binding protein that binds to both mRNA and 18 S rRNA simultaneously (2,3). It interacts with the ribosome-bound eIF3 through protein-protein interactions (4).…”

Poly(U) binding activity of hepatitis C virus NS3 protein, a putative RNA helicase

“…This suggests that the gel shift assay may be useful for detecting potential regions of RNA binding activity, but this region was not always responsible for activity in the whole RNA-binding molecule. Recently, the RNA binding activity of the cellular helicase, eIF-4B [12] and viral heli- cases [10,13] has been detected by using a filter-binding assay. However, the binding specificity remains unclear.…”