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. 2002 Apr 16;99(8):5301–5306. doi: 10.1073/pnas.082107599

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Copyright © 2002, The National Academy of Sciences

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Comparative dicistronic analysis of IRES activities of multiple G(A)₃ modules and natural IRESs (IRES and IRES^EMCV) in WGE (A), tobacco protoplasts (B), and HeLa cells (C). Artificial sequences tested: (i) (PPT₁₉)₄ and (PPT₁₉)₈ representing the tandem repeats of four (76-nt) and eight (152-nt) copies of the 19-nt AAAAGAAGGAAAAAGAAGG sequence derived from PPT₃₂ (see Fig. 3), respectively; (ii) the 64-nt (GAAA)₁₆ sequence consisting of 16 G(A)₃ elements; (iii) control U-rich sequence (GUUU)₁₆; (iv) the control Emp × 4 sequence consisting of four copies of the U-rich CGUUUGCUUUUUGUAGUA element derived from another crTMV IRES (IRES) and (v) the GCU-rich sequence (GCU-R) containing four copies of CGCGGGCG blocks linked via the 7-nt sequence UUUGUUU used as an additional negative control. (A) Analysis of proteins directed in WGE by dicistronic H-GFP-ICS-GUS T7 transcripts containing artificial sequences as the intercistronic spacer. Arrows indicate the position of GUS and GFP. (B and C) GUS gene expression in tobacco protoplasts (B) and HeLa (C) cells transfected with dicistronic GFP-IRES-GUS constructs containing different IRES sequences. “Mock” indicates that DNA-free solution was used for transfection.

Inline graphic — Comparative dicistronic analysis of IRES activities of multiple G(A)₃ modules and natural IRESs (IRES and IRES^EMCV) in WGE (A), tobacco protoplasts (B), and HeLa cells (C). Artificial sequences tested: (i) (PPT₁₉)₄ and (PPT₁₉)₈ representing the tandem repeats of four (76-nt) and eight (152-nt) copies of the 19-nt AAAAGAAGGAAAAAGAAGG sequence derived from PPT₃₂ (see Fig. 3), respectively; (ii) the 64-nt (GAAA)₁₆ sequence consisting of 16 G(A)₃ elements; (iii) control U-rich sequence (GUUU)₁₆; (iv) the control Emp × 4 sequence consisting of four copies of the U-rich CGUUUGCUUUUUGUAGUA element derived from another crTMV IRES (IRES) and (v) the GCU-rich sequence (GCU-R) containing four copies of CGCGGGCG blocks linked via the 7-nt sequence UUUGUUU used as an additional negative control. (A) Analysis of proteins directed in WGE by dicistronic H-GFP-ICS-GUS T7 transcripts containing artificial sequences as the intercistronic spacer. Arrows indicate the position of GUS and GFP. (B and C) GUS gene expression in tobacco protoplasts (B) and HeLa (C) cells transfected with dicistronic GFP-IRES-GUS constructs containing different IRES sequences. “Mock” indicates that DNA-free solution was used for transfection.