Pseudohyphenation. (A) Adhesion of haploid eIF4E cap-binding mutants E103Q, E105Q, D106N and E107Q in comparison to eIF4E wt. Plates were incubated at 30u or 35uC for 2 days, then washed under a gentle stream of water. (B) Pseudohyphenation of diploid eIF4E cap-binding mutants in comparison to eIF4E wt. Cells were incubated on SLAD50 plates at 30uC for 2 days; shown is a 2006 or 406 magnification of cells. (C) ?Galactosidase activity expressed from Flo11-LacZ in haploid eIF4E wt and mutants E103Q, E105Q, D106N and E107Q. Expression levels were JSI124 normalized to LacZ mRNA content which was determined by quantitative RT-PCR. (D) Western Blot of eIF4E mutants. Blot of total extracts used for incubation with m7GDP-agarose (1/20 volume input; 50 mg total protein); lower panel: Blot of eluted eIF4E (1/1 volume). Intensity of eIF4E signals was analysed by ImageJ. Protein inputs for the upper blot were normalized with the help of a polyclonal antibody against carboxypeptidase Y (Prc1p; not shown), numbers represent the relative eIF4E content as compared to wt protein. Eluted eIF4E bands were furthermore normalized against total eIF4E input as determined for each extract (in blue). Asterix indicates an BI-78D3 unspecific band. doi:10.1371/journal.pone.0050773.geIF4E’s Role in AdhesionFigure 3. eIF4E mutants W75A (affecting p20 interaction) or a knockout of p20 do not loose adhesion and pseudohyphenation. (A) Adhesion of haploid eIF4E mutants W75A or Dp20 as compared to eIF4E wt. Plates were incubated at 30u or 35uC for 2 days, then washed under a gentle stream of water. (B) Pseudohyphenation of diploid eIF4E W75A or Dp20 in comparison to eIF4E wt. Cells were incubated on SLAD50 plates at 30uC for 2 days; shown is a 2006 or 406 magnification of cells. (C) ?Galactosidase activity expressed from Flo11-LacZ in haploid eIF4E wt and mutants W75A and Dp20. Expression levels were normalized to LacZ mRNA content which was determined by quantitative RT-PCR. (D) Western Blots of eIF4E wt, W75A or Dp20. Top panel: Blot of extract used for binding to m7GDP-Agarose (1/20 volume of input, 50 mg total protein each lane); lower panel: Blot of total eIF4E bound to m7GDP-Agarose (1 mg input), additional decoration with polyclonal antibody against p20. Intensity of eIF4E signals was analysed by ImageJ. Protein inputs for the upper blot were normalized with the help of a polyclonal antibody against carboxypeptidase Y (Prc1p; not shown), numbers represent the relative eIF4E content as compared to wt protein. Eluted eIF4E bands were furthermore normalized against total eIF4E input as determined 1407003 for each extract (in blue). Asterix indicates an unspecific band. Signal strength of p20 is indicated in cursive numbers. doi:10.1371/journal.pone.0050773.geIF4E’s Role in AdhesionResults Temperature-sensitive eIF4E Yeast Mutants Loose Adhesion and do not PseudohyphenateUsing plasmid shuffling techniques (see Table S3; Material and Methods) we introduced eIF4E-mutations ts4-2 (G179D/E73K), ts4-3 (G179D/E103K) and cdc33-1 (G113D) into the adhesive haploid yeast strain RH2585 (see Table S2). They all render a temperature-sensitive phenotype (no growth at 37uC; see Figure S1) [4]. As shown in Figure 1A, ts-strains grown for 2? days on full medium at two different temperatures (they still grow at 35uC, though rather slowly) almost completely lost adhesion when compared to the isogenic strain carrying wt (wild type) eIF4E. We confirmed the presence of eIF4E protein by SDS-PAGE and Western Blott.Pseudohyphenation. (A) Adhesion of haploid eIF4E cap-binding mutants E103Q, E105Q, D106N and E107Q in comparison to eIF4E wt. Plates were incubated at 30u or 35uC for 2 days, then washed under a gentle stream of water. (B) Pseudohyphenation of diploid eIF4E cap-binding mutants in comparison to eIF4E wt. Cells were incubated on SLAD50 plates at 30uC for 2 days; shown is a 2006 or 406 magnification of cells. (C) ?Galactosidase activity expressed from Flo11-LacZ in haploid eIF4E wt and mutants E103Q, E105Q, D106N and E107Q. Expression levels were normalized to LacZ mRNA content which was determined by quantitative RT-PCR. (D) Western Blot of eIF4E mutants. Blot of total extracts used for incubation with m7GDP-agarose (1/20 volume input; 50 mg total protein); lower panel: Blot of eluted eIF4E (1/1 volume). Intensity of eIF4E signals was analysed by ImageJ. Protein inputs for the upper blot were normalized with the help of a polyclonal antibody against carboxypeptidase Y (Prc1p; not shown), numbers represent the relative eIF4E content as compared to wt protein. Eluted eIF4E bands were furthermore normalized against total eIF4E input as determined for each extract (in blue). Asterix indicates an unspecific band. doi:10.1371/journal.pone.0050773.geIF4E’s Role in AdhesionFigure 3. eIF4E mutants W75A (affecting p20 interaction) or a knockout of p20 do not loose adhesion and pseudohyphenation. (A) Adhesion of haploid eIF4E mutants W75A or Dp20 as compared to eIF4E wt. Plates were incubated at 30u or 35uC for 2 days, then washed under a gentle stream of water. (B) Pseudohyphenation of diploid eIF4E W75A or Dp20 in comparison to eIF4E wt. Cells were incubated on SLAD50 plates at 30uC for 2 days; shown is a 2006 or 406 magnification of cells. (C) ?Galactosidase activity expressed from Flo11-LacZ in haploid eIF4E wt and mutants W75A and Dp20. Expression levels were normalized to LacZ mRNA content which was determined by quantitative RT-PCR. (D) Western Blots of eIF4E wt, W75A or Dp20. Top panel: Blot of extract used for binding to m7GDP-Agarose (1/20 volume of input, 50 mg total protein each lane); lower panel: Blot of total eIF4E bound to m7GDP-Agarose (1 mg input), additional decoration with polyclonal antibody against p20. Intensity of eIF4E signals was analysed by ImageJ. Protein inputs for the upper blot were normalized with the help of a polyclonal antibody against carboxypeptidase Y (Prc1p; not shown), numbers represent the relative eIF4E content as compared to wt protein. Eluted eIF4E bands were furthermore normalized against total eIF4E input as determined 1407003 for each extract (in blue). Asterix indicates an unspecific band. Signal strength of p20 is indicated in cursive numbers. doi:10.1371/journal.pone.0050773.geIF4E’s Role in AdhesionResults Temperature-sensitive eIF4E Yeast Mutants Loose Adhesion and do not PseudohyphenateUsing plasmid shuffling techniques (see Table S3; Material and Methods) we introduced eIF4E-mutations ts4-2 (G179D/E73K), ts4-3 (G179D/E103K) and cdc33-1 (G113D) into the adhesive haploid yeast strain RH2585 (see Table S2). They all render a temperature-sensitive phenotype (no growth at 37uC; see Figure S1) [4]. As shown in Figure 1A, ts-strains grown for 2? days on full medium at two different temperatures (they still grow at 35uC, though rather slowly) almost completely lost adhesion when compared to the isogenic strain carrying wt (wild type) eIF4E. We confirmed the presence of eIF4E protein by SDS-PAGE and Western Blott.
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