Eukaryotic initiation factor 4A-I (also known as eIF4A1 or DDX2A) is a 46 kDa cytosolic protein that, in humans, is encoded by the EIF4A1 gene, which is located on chromosome 17. It is the most prevalent member of the eIF4A family of ATP-dependant RNA helicases, and plays a critical role in the initiation of cap-dependent eukaryotic protein translation as a component of the eIF4F translation initiation complex. eIF4A1 unwinds the secondary structure of RNA within the 5'-UTR of mRNA, a critical step necessary for the recruitment of the 43S preinitiation complex, and thus the translation of protein in eukaryotes. eIF4A1 is an ATP-dependent RNA helicase, however the exact nature of its dependence on ATP for its function is still debated. Although after ATP binding, the subsequent hydrolysis induces conformational changes in eIF4A1, other DEAD-box RNA helicases have been shown to possess helicase activity in the presence of nonhydrolyzable analogues of ATP, suggesting that binding, and not hydrolysis, is the more important element in regulating activity. eIF4A1 is a component of the eIF4F translation initiation complex, along with eIF4E, the 5'-terminal cap binding protein, and eIF4G, the scaffold protein that holds eIF4A and eIF4E together. The eIF4F complex is often accompanied by the accessory proteins eIF4B and eIF4H, either of which can differentially enhance the activity of eIF4A1. After mRNA is transcribed from DNA and translocated to the cytoplasm, and the cytosolic PABP is bound to the Poly(A)-tail of the nascent mRNA, its 5'-cap will bind to eIF4E and PABP will bind to eIF4G. eIF4A1 will then unwind the RNA secondary structure from 5' to 3' as the 43S PIC is recruited to the eIF4F complex. The 43S PIC will scan the unwound mRNA from 5' to 3' as well, until it reaches the AUG start codon, whereupon the 60S ribosomal subunit will be recruited to begin the process of elongation.
Background References
1. Raman D et al. Role of eIF4A1 in triple-negative breast cancer stem-like cell-mediated drug resistance. Cancer Rep (Hoboken). 2022 Dec
2. Zhang LL et al. High expression of eIF4A1 predicts unfavorable prognosis in clear cell renal cell carcinoma. Mol Cell Probes. 2022 Oct
Western blot analysis of eIF4A1 on different lysates with Rabbit anti-eIF4A1 antibody (HA721430) at 1/1,000 dilution.
Lane 1: HeLa cell lysate Lane 2: U-2 OS cell lysate Lane 3: K-562 cell lysate Lane 4: HEK-293 cell lysate Lane 5: MCF7 cell lysate Lane 6: HepG2 cell lysate Lane 7: Huh7 cell lysate Lane 8: Jurkat cell lysate Lane 9: PC-12 cell lysate
Lysates/proteins at 15 µg/Lane.
Predicted band size: 46 kDa Observed band size: 46 kDa
Exposure time: 3 minutes;
4-20% SDS-PAGE gel.
Proteins were transferred to a PVDF membrane and blocked with 5% NFDM/TBST for 1 hour at room temperature. The primary antibody (HA721430) at 1/1,000 dilution was used in 5% NFDM/TBST at room temperature for 2 hours. Goat Anti-Rabbit IgG - HRP Secondary Antibody (HA1001) at 1:100,000 dilution was used for 1 hour at room temperature.
Immunohistochemical analysis of paraffin-embedded mouse colon tissue with Rabbit anti-eIF4A1 antibody (HA721430) at 1/200 dilution.
The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes. The tissues were blocked in 1% BSA for 20 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (HA721430) at 1/200 dilution for 1 hour at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunocytochemistry analysis of HeLa cells labeling eIF4A1 with Rabbit anti-eIF4A1 antibody (HA721430) at 1/100 dilution.
Cells were fixed in 4% paraformaldehyde for 10 minutes at 37 ℃, permeabilized with 0.05% Triton X-100 in PBS for 20 minutes, and then blocked with 2% negative goat serum for 30 minutes at room temperature. Cells were then incubated with Rabbit anti-eIF4A1 antibody (HA721430) at 1/100 dilution in 2% negative goat serum overnight at 4 ℃. Goat Anti-Rabbit IgG H&L (iFluor™ 488, HA1121) was used as the secondary antibody at 1/1,000 dilution. Nuclear DNA was labelled in blue with DAPI.
Beta tubulin (M1305-2, red) was stained at 1/200 dilution overnight at +4℃. Goat Anti-Mouse IgG H&L (iFluor™ 594, HA1126) was used as the secondary antibody at 1/1,000 dilution.
Flow cytometric analysis of HeLa cells labeling eIF4A1.
Cells were fixed and permeabilized. Then stained with the primary antibody (HA721430, 1ug/ml) (red) compared with Rabbit IgG Isotype Control (green). After incubation of the primary antibody at +4℃ for an hour, the cells were stained with a iFluor™ 488 conjugate-Goat anti-Rabbit IgG Secondary antibody (HA1121) at 1/1,000 dilution for 30 minutes at +4℃. Unlabelled sample was used as a control (cells without incubation with primary antibody; black).
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