DEAH Box Polypeptide 29 (DHX29)

The 43S preinitiation complex containing 40S ribosomal subunits, EIF3, EIF2, EIF1, EIF1A (EIF1AX), and initiator tRNA binds to and scans 5-prime UTRs of mRNAs to identify the initiation codon, where it stops to form the 48S initiation complex. Scanning of unstructured 5-prime UTRs does not require ATP or factors associated with ATP hydrolysis and RNA unwinding, whereas scanning of 5-prime UTRs with even weak secondary structure requires ATP and EIF4A, EIF4G, and EIF4B. Dhx29 bound 40S ribosomal subunits and hydrolyzed ATP, GTP, UTP, and CTP. NTPase activity of Dhx29 was strongly stimulated by 43S complexes, and Dhx29 stimulated 48S complex formation most strongly when it was present in substoichiometric amounts relative to 43S complexes. Rabbit Dhx29 did not show processive helicase activity.