Pioneer round of translation occurs during serum starvation.
The pioneer round of translation plays a role in translation initiation of newly spliced and exon junction complex (EJC)-bound mRNAs. Nuclear cap-binding protein complex CBP80/20 binds to those mRNAs at the 5'-end, recruiting translation initiation complex. As a consequence of the pioneer round of translation, the bound EJCs are dissociated from mRNAs and CBP80/20 is replaced by the cytoplasmic cap-binding protein eIF4E. Steady-state translation directed by eIF4E allows for an immediate and rapid response to changes in physiological conditions. Here, we show that nonsense-mediated mRNA decay (NMD), which restricts only to the pioneer round of translation but not to steady-state translation, efficiently occurs even during serum starvation, in which steady-state translation is drastically abolished. Accordingly, CBP80 remains in the nucleus and processing bodies are unaffected in their abundance and number in serum-starved conditions. These results suggest that mRNAs enter the pioneer round of translation during serum starvation and are targeted for NMD if they contain premature termination codons.
Oh
Nara
N
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
Kim
Kyoung Mi
KM
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
Cho
Hana
H
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
Choe
Junho
J
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
Kim
Yoon Ki
YK
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea. Electronic address: yk-kim@korea.ac.kr.
D003062:Codon; D016895:Culture Media, Serum-Free / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000737:chemistry; D005091:Exons; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D039502:Nuclear Cap-Binding Protein Complex / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry
D003062:Codon; D016895:Culture Media, Serum-Free; D039561:Eukaryotic Initiation Factor-4E; D039502:Nuclear Cap-Binding Protein Complex; D010455:Peptides; D012333:RNA, Messenger