Phosphate buffer, 500 mM NaCl, 30 mM imidazole, 5 glycerol and 0.5 mM TCEP at a flow rate of 1.0 ml/min. Bound proteins were eluted with 50 mM sodium phosphate buffer, 500 mM NaCl, 250 mM imidazole, 5 glycerol and 0.5 mM TCEP at a flow price of 1.0 ml/min. In a final step eluted proteins were subjected to a size exclusion column applying a Superdex 10/300 column that was run with 50 mM sodium phosphate buffer, 50 mM NaCl and five glycerol at a flow rate of 0.five ml/min. Fractions and purified proteins have been separated on 8 PAA gels and colloidial or silver stained. Complete purification was conducted on an Ackta FPLC technique. To identify protein concentration spectrophotometric measurements had been carried out with a Nanodrop. Image processing of colloidial stainings was carried out with Photoshop 7.0. tubulin and histone H3. Coimmunoprecipitation of recombinant proteins The association between recombinant hnRNP R and SMN was analyzed by coimmunoprecipitation using GammaBind Plus Sepharose beads. 250 or 500 ng of rhnRNP R and 250 ng of rSMN had been incubated in binding buffer, comprising 50 mM sodium phosphate, 5 glycerol, 50 mM NaCl and 0.1 Tween, with 20 ml Sepharose beads and 1 mg antibodies against hnRNP R, SMN or non-specific IgG handle for 1 h at RT. The resin was washed 5 occasions with binding buffer to take away unbound proteins. For elution beads have been boiled in 2xLaemmli buffer at 95uC for five min. The eluted proteins have been then analyzed by Western blotting. Notably, Light chain-specific C.I. 42053 site secondary antibodies were applied for detection because the 55 kDa heavy chain in the immunoprecipitation would mask the SMN signal. Subcellular fractionation of mouse motoneurons At least one hundred 000 major motoneurons have been plated on a 12-well cell culture dish and cultured for 7DIV in the presence of ten ng/ ml BDNF and CNTF. Buffers for fractionation have been ready freshly and 
filtered having a 0.45 mm filter. Cells were washed three occasions with ice-cold PBS. Motoneurons had been lysed with all the Tat-NR2B9c web cytoplasmic fractionation buffer containing 50 mM Tris, 150 mM NaCl, 0.1 NP-40, 1 mM MgCl2 and 1x Complete Protease inhibitor for 10 min on ice. Cells were scrapped off completely and centrifuged at 500 g for 10 min at 4uC. The supernatant, i.e. the cytoplasmic fraction, was collected. The pellet was washed three occasions with 25 ml cytoplasmic buffer to eliminate the remaining cytoplasmic fraction. Supernatants had been collected and added to the current cytoplasmic fraction. The pellet was lysed with nuclear fractionation buffer comprising 20 mM HEPES, 400 mM NaCl, 1 mM EDTA, 0.5 mM NaF, 0.five mM DTT, two.5 Glycerol, 0.6 CHAPS, two U/ 100 ml Benzonase and 1x Total Protease Inhibitor PubMed ID:http://jpet.aspetjournals.org/content/128/2/107 for three min on ice. The fraction was homogenized, incubated for ten min on ice and centrifuged at 5000 g for 10 min at 4uC. The supernatant, i.e. the soluble nuclear fraction, was collected. Total protein concentration of nuclear and cytosolic fractions was assessed employing the Pierce BCA Protein Assay Kit. Equal amounts of proteins were loaded for Western Blot analyses. Cytoplasmic and nuclear fractions have been controlled employing antibodies against GAPDH, a tubulin and histone H3. Immunoprecipitation Spinal cord without the need of vertebra isolated from E18 mouse embryo or about 500 000 major motoneurons cultured for 7DIV were employed for coimmunoprecipitation experiments. Nuclear and cytoplasmic proteins were extracted. Fractions were pre-cleaned with protein G beads and protein A beads for 1 h. Afterwards, the pre-cleaned lysa.Phosphate buffer, 500 mM NaCl, 30 mM imidazole, five glycerol and 0.five mM TCEP at a flow price of 1.0 ml/min. Bound proteins have been eluted with 50 mM sodium phosphate buffer, 500 mM NaCl, 250 mM imidazole, 5 glycerol and 0.5 mM TCEP at a flow rate of 1.0 ml/min. In a final step eluted proteins had been subjected to a size exclusion column working with a Superdex 10/300 column that was run with 50 mM sodium phosphate buffer, 50 mM NaCl and five glycerol at a flow rate of 0.five ml/min. Fractions and purified proteins were separated on 8 PAA gels and colloidial or silver stained. Complete purification was conducted on an Ackta FPLC method. To figure out protein concentration spectrophotometric measurements have been carried out with a Nanodrop. Image processing of colloidial stainings was carried out with Photoshop 7.0. tubulin and histone H3. Coimmunoprecipitation of recombinant proteins The association amongst recombinant hnRNP R and SMN was analyzed by coimmunoprecipitation working with GammaBind Plus Sepharose beads. 250 or 500 ng of rhnRNP R and 250 ng of rSMN were incubated in binding buffer, comprising 50 mM sodium phosphate, 5 glycerol, 50 mM NaCl and 0.1 Tween, with 20 ml Sepharose beads and 1 mg antibodies against hnRNP R, SMN or non-specific IgG manage for 1 h at RT. The resin was washed 5 occasions with binding buffer to remove unbound proteins. For elution beads had been boiled in 2xLaemmli buffer at 95uC for five min. The eluted proteins had been then analyzed by Western blotting. Notably, Light chain-specific secondary antibodies have been used for detection since the 55 kDa heavy chain from the immunoprecipitation would mask the SMN signal. Subcellular fractionation of mouse motoneurons At least one hundred 000 main motoneurons had been plated on a 12-well cell culture dish and cultured for 7DIV within the presence of 10 ng/ ml BDNF and CNTF. Buffers for fractionation have been ready freshly and filtered with a 0.45 mm filter. Cells had been washed three occasions with ice-cold PBS. Motoneurons were lysed together with the cytoplasmic fractionation buffer containing 50 mM Tris, 150 mM NaCl, 0.1 NP-40, 1 mM MgCl2 and 1x Full Protease inhibitor for ten min on ice. Cells were scrapped off thoroughly and centrifuged at 500 g for ten min at 4uC. The supernatant, i.e. the cytoplasmic fraction, was collected. The pellet was washed 3 occasions with 25 ml cytoplasmic buffer to eliminate the remaining cytoplasmic fraction. Supernatants were collected and added to the existing cytoplasmic fraction. The pellet was lysed with nuclear fractionation buffer comprising 20 mM HEPES, 400 mM NaCl, 1 mM EDTA, 0.5 mM NaF, 0.five mM DTT, 2.5 Glycerol, 0.six CHAPS, 2 U/ 100 ml Benzonase and 1x Total Protease Inhibitor PubMed ID:http://jpet.aspetjournals.org/content/128/2/107 for 3 min on ice. 
The fraction was homogenized, incubated for 10 min on ice and centrifuged at 5000 g for 10 min at 4uC. The supernatant, i.e. the soluble nuclear fraction, was collected. Total protein concentration of nuclear and cytosolic fractions was assessed employing the Pierce BCA Protein Assay Kit. Equal amounts of proteins were loaded for Western Blot analyses. Cytoplasmic and nuclear fractions have been controlled employing antibodies against GAPDH, a tubulin and histone H3. Immunoprecipitation Spinal cord with out vertebra isolated from E18 mouse embryo or approximately 500 000 major motoneurons cultured for 7DIV were used for coimmunoprecipitation experiments. Nuclear and cytoplasmic proteins had been extracted. Fractions had been pre-cleaned with protein G beads and protein A beads for 1 h. Afterwards, the pre-cleaned lysa.