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Up-regulation of PDCD4 in senescent human diploid fibroblasts
Min-Ji Kang1, Hye-Sung Ahn, Ji-Young Lee
1Department of Biochemistry and Molecular Biology and Ilchun Molecular Medicine Institute, Seoul National University College of Medicine, 28 Yongondong, Chongnogu, Seoul 110-799, Republic of Korea.
Abstract:
Programmed cell death 4 (PDCD4) has a common MI domain sharing with death associated protein 5 (DAP5) and a component of eukaryotic translation initiation factor (eIF4G) complex and it might also work as a tumor suppressor. We could find that the message and product of Pdcd4 gene were up-regulated in senescent human diploid fibroblasts. In yeast two hybrid analysis, the C-terminal region of PDCD4 interacted with ribosomal protein S13 (RPS13), ribosomal protein L5 (RPL5), and TI-227H. In in vitro binding assay, RPS13, a component of 40S ribosome was stably bound to PDCD4. We also found that PDCD4 was localized to polysome fractions. We could pull out eIF4G with GST-PDCD4, but eIF4E did not interact with PDCD4. From these results, we could assume that PDCD4 might regulate the eIF4G-dependent translation through direct interactions with eIF4G and RPS13 in senescent fibroblasts.
Insights
Programmed cell death 4 (PDCD4) is upregulated in senescent cells and binds to ribosomal protein S13 (RPS13). PDCD4 may regulate translation via interactions with eIF4G and RPS13 in senescent fibroblasts.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Programmed cell death 4 (PDCD4) shares domains with DAP5 and is part of the eIF4G complex.
- PDCD4 is implicated as a potential tumor suppressor.
- PDCD4's role in cellular processes, particularly senescence, requires further elucidation.
Purpose of the Study:
- To investigate the expression and function of PDCD4 in senescent human diploid fibroblasts.
- To identify proteins that interact with PDCD4.
- To explore the mechanism by which PDCD4 influences translation during senescence.
Main Methods:
- Yeast two-hybrid analysis to identify PDCD4 interacting partners.
- In vitro binding assays to confirm protein interactions.
- Analysis of PDCD4 localization within cellular fractions (polysomes).
- GST pull-down assays to assess interactions with translation factors.
Main Results:
- PDCD4 gene expression and protein levels were elevated in senescent fibroblasts.
- PDCD4 interacted with ribosomal proteins RPS13 and RPL5, and TI-227H.
- In vitro assays confirmed stable binding between PDCD4 and RPS13.
- PDCD4 was found in polysome fractions, indicating involvement in active translation.
- PDCD4 interacted with eIF4G but not eIF4E.
Conclusions:
- PDCD4 is upregulated during cellular senescence.
- PDCD4 directly interacts with ribosomal protein RPS13 and translation factor eIF4G.
- These interactions suggest PDCD4 plays a role in regulating eIF4G-dependent translation in senescent cells.