A novel eIF5A complex functions as a regulator of p53 and p53-dependent apoptosis.
Although eukaryotic translation initiation factor 5A (eIF5A) was originally designated as an "initiation factor," recent data have shown it to be also involved in apoptosis. However, the actual function of eIF5A in apoptosis is still unknown. In this study, we performed yeast two-hybrid screens to identify eIF5A-interacting proteins to help us understand the mechanisms of eIF5A. Our results demonstrated that eIF5A and syntenin could engage in a specific interaction both in vitro and in vivo and functioned collaboratively to regulate p53 activity. Our findings, for the first time, revealed a new biological activity for eIF5A as the regulator of p53. Overexpression of eIF5A or its EFP domain resulted in up-regulation of p53, and silencing eIF5A by small interfering RNA reduced the p53 protein level. Further analysis by reverse transcription PCR showed eIF5A-activated p53 transcription. The effect of eIF5A on p53 transcriptional activity was further demonstrated by the increasing expressions of p21 and Bax, well known target genes of p53. In contrast, a point mutant of eIF5A, hypusination being abolished, was revealed to be functionally defective in p53 up-regulation. Overexpression of eIF5A led to a p53-dependent apoptosis or sensitized cells to induction of apoptosis by chemotherapeutic agents. However, when eIF5A interacted with its novel partner, syntenin, the eIF5A-induced increase in p53 protein level was significantly inhibited. Therefore, eIF5A seems to be a previously unrecognized regulator of p53 that may define a new pathway for p53-dependent apoptosis, and syntenin might regulate p53 by balancing the regulation of eIF5A signaling to p53 for apoptosis.
Li
Ai-Ling
AL
Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China.
Li
Hui-Yan
HY
Jin
Bao-Feng
BF
Ye
Qi-Nong
QN
Zhou
Tao
T
Yu
Xiao-Dan
XD
Pan
Xin
X
Man
Jiang-Hong
JH
He
Kun
K
Yu
Ming
M
Hu
Mei-Ru
MR
Wang
Jie
J
Yang
Song-Cheng
SC
Shen
Bei-Fen
BF
Zhang
Xue-Min
XM
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000378:metabolism; D005434:Flow Cytometry; D031541:Fluorescence Resonance Energy Transfer; D005786:Gene Expression Regulation; D020868:Gene Silencing; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D009154:Mutation; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000502:physiology*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053676:Syntenins; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein; D000097574:Eukaryotic Translation Initiation Factor 5A
D018076:DNA, Complementary; D005982:Glutathione Transferase; D049452:Green Fluorescent Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010448:Peptide Initiation Factors; D019253:Proto-Oncogene Proteins c-bcl-2; D016283:Proto-Oncogene Proteins p21(ras); D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D053676:Syntenins; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D000097574:Eukaryotic Translation Initiation Factor 5A; C494826:BAX protein, human; C109621:SDCBP protein, human; C501009:HRAS protein, human