Transient idling of posttermination ribosomes ready to reinitiate protein synthesis.
The fate of ribosomes between termination and initiation during protein synthesis is very basic, yet poorly understood. Here we found that translational reinitiation of the alkaline phosphatase gene occurs in Escherichia coli from an internal methionine codon when the authentic translation is prematurely terminated at a nonsense codon that is within seven codons upstream of the reinitiation codon (which we refer to as "reinitiation window"). Changing the reading frame downstream of the stop codon did not abolish the reinitiation, while inactivating the upstream initiation codon abolished the reinitiation. Moreover, depletion of the ribosome recycling factor (RRF), which disassembles posttermination ribosomes in conjunction with elongation factor G, did not influence the observed reinitiation. These findings suggest that posttermination ribosomes can undergo a transient idling state ready to reinitiate protein synthesis even in the absence of the Shine-Dalgarno (SD) sequence within the reinitiation window by evading disengagement from the mRNA.
Karamyshev
Andrey L
AL
Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
Karamysheva
Zemfira N
ZN
Yamami
Tohru
T
Ito
Koichi
K
Nakamura
Yoshikazu
Y
D000469:Alkaline Phosphatase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003062:Codon; D018387:Codon, Initiator; D018389:Codon, Nonsense; D018388:Codon, Terminator; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D010442:Peptide Chain Initiation, Translational; D010443:Peptide Chain Termination, Translational; D010957:Plasmids; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D013462:Sulfur Radioisotopes / Q000378:metabolism
D003062:Codon; D018387:Codon, Initiator; D018389:Codon, Nonsense; D018388:Codon, Terminator; D012333:RNA, Messenger; D013462:Sulfur Radioisotopes; D008715:Methionine; D000469:Alkaline Phosphatase