F PRMT6-dependent H3R2 methylation at the promoter level [19,20]. The same mechanism of repression has been demonstrated towards p53 [22], clearly linking PRMT6 with the process of tumorigenesis. The rapidly growing importance of PRMT6 highlights the need to investigate more deeply the mechanisms this enzyme is involved in. We adopted the yeast-two hybrid (Y2H) assay to obtain a protein network providing a more detailed picture of the molecular context in which PRMT6 is embedded. Moreover, we demonstrated the utility of this molecular network 
in supporting the set-up of hypothesis-driven experiments. Indeed, both new connections and modulatory mechanisms within the PRMT6 molecular network have been highlighted.as a template as described in Materials and Methods S1. The human fetal brain cDNA library in the pJG4-5 plasmid was a kind gift of Dr. G. Del Sal. pGEX4T-2 HMGA1b, pGEX4T-2 HMGA2, pGEX-6P-1 PRMT6, and pGEX2T-GAR have been described previously [23,5,24]. Each putative partner was subcloned between the EcoRI and XhoI sites of the vectors pcDNA3HA and pGEX4T-1. The mammalian expression vector pcDNA3MBP-PRMT6 was generated by subcloning PRMT6 from pGEX6P-1 PRMT6 in the BamHI and XhoI sites of pcDNA3MBP (kindly provided by Dr. L. Collavin). All the tags are in fusion with the N-terminal portion of the proteins. Plasmids pARHMGA1a, pARHMGA1a-(1?2), and pARHMGA1aR57,59A for the expression of wild-type and mutant forms of human HMGA1a proteins were previously described [11].Yeast Two-hybrid Screening Materials and Methods PlasmidsPlasmids pEG202 PRMT6/1-86,/1-184,/87-184,/87-375, and/185-375, expressing deletion mutants of human PRMT6 protein, were generated by PCR using the human PRMT6 cDNA pEG202-PRMT6 vector was used to express wild type PRMT6 linked to the C-terminus of LexA DNA-binding domain. Recombinant plasmid was transfected in Saccaromyces cerevisiae strain EGY48 (MATa, Trp1, Ura3, His3, LEU2::LexAop6LEU2). A human fetal brain cDNA library expressing Gal4 activation domain fusion proteins was transfected in the yeast strainFigure 1. PRMT6 protein-protein 166518-60-1 web interaction domain maps mainly to the N-terminal protein portion 1?6. (A) Schematic representation of the PRMT6 deletion mutants. The central region containing the catalytic domain is indicated in black. Numbers correspond to the aminoacids positions. Positive interactions out of 31 partners tested are indicated on the right. (B) Total protein extracts from yeast expressing the different PRMT6 deletion mutants in fusion with LexA DNA binding domain, grown in medium containing glucose (Glu) or galactose and raffinose (Gal/Raf), were separated in SDS-PAGE (T = 10 ) and analyzed by western blot using an a-LexA antibody. Molecular weights are indicated on the left. doi:10.1371/journal.pone.0053750.gThe Protein-Protein Molecular Network of PRMTcontaining pEG202-PRMT6 for a screening assay. A total of ,6.46106 transformants were plated on Complete Minimal (CM) medium supplemented with galactose/raffinose, lacking ��-Sitosterol ��-D-glucoside cost histidine, tryptophan, uracile and leucine. After 4 days, clones were tested by a b-galactosidase filter assay. Among these, 360 were tested in a secondary screening. For this purpose the plasmid coding for each putative partner was extracted and used to transform E. coli strain B290 with electroporation. For each transformation 3 different colonies were analyzed and positive plasmids were re-transformed into EGY48 
with pEG202-PRMT6; 179 clones were confirmed to be Leu+ and.F PRMT6-dependent H3R2 methylation at the promoter level [19,20]. The same mechanism of repression has been demonstrated towards p53 [22], clearly linking PRMT6 with the process of tumorigenesis. The rapidly growing importance of PRMT6 highlights the need to investigate more deeply the mechanisms this enzyme is involved in. We adopted the yeast-two hybrid (Y2H) assay to obtain a protein network providing a more detailed picture of the molecular context in which PRMT6 is embedded. Moreover, we demonstrated the utility of this molecular network in supporting the set-up of hypothesis-driven experiments. Indeed, both new connections and modulatory mechanisms within the PRMT6 molecular network have been highlighted.as a template as described in Materials and Methods S1. The human fetal brain cDNA library in the pJG4-5 plasmid was a kind gift of Dr. G. Del Sal. pGEX4T-2 HMGA1b, pGEX4T-2 HMGA2, pGEX-6P-1 PRMT6, and pGEX2T-GAR have been described previously [23,5,24]. Each putative partner was subcloned between the EcoRI and XhoI sites of the vectors pcDNA3HA and pGEX4T-1. The mammalian expression vector pcDNA3MBP-PRMT6 was generated by subcloning PRMT6 from pGEX6P-1 PRMT6 in the BamHI and XhoI sites of pcDNA3MBP (kindly provided by Dr. L. Collavin). All the tags are in fusion with the N-terminal portion of the proteins. Plasmids pARHMGA1a, pARHMGA1a-(1?2), and pARHMGA1aR57,59A for the expression of wild-type and mutant forms of human HMGA1a proteins were previously described [11].Yeast Two-hybrid Screening Materials and Methods PlasmidsPlasmids pEG202 PRMT6/1-86,/1-184,/87-184,/87-375, and/185-375, expressing deletion mutants of human PRMT6 protein, were generated by PCR using the human PRMT6 cDNA pEG202-PRMT6 vector was used to express wild type PRMT6 linked to the C-terminus of LexA DNA-binding domain. Recombinant plasmid was transfected in Saccaromyces cerevisiae strain EGY48 (MATa, Trp1, Ura3, His3, LEU2::LexAop6LEU2). A human fetal brain cDNA library expressing Gal4 activation domain fusion proteins was transfected in the yeast strainFigure 1. PRMT6 protein-protein interaction domain maps mainly to the N-terminal protein portion 1?6. (A) Schematic representation of the PRMT6 deletion mutants. The central region containing the catalytic domain is indicated in black. Numbers correspond to the aminoacids positions. Positive interactions out of 31 partners tested are indicated on the right. (B) Total protein extracts from yeast expressing the different PRMT6 deletion mutants in fusion with LexA DNA binding domain, grown in medium containing glucose (Glu) or galactose and raffinose (Gal/Raf), were separated in SDS-PAGE (T = 10 ) and analyzed by western blot using an a-LexA antibody. Molecular weights are indicated on the left. doi:10.1371/journal.pone.0053750.gThe Protein-Protein Molecular Network of PRMTcontaining pEG202-PRMT6 for a screening assay. A total of ,6.46106 transformants were plated on Complete Minimal (CM) medium supplemented with galactose/raffinose, lacking histidine, tryptophan, uracile and leucine. After 4 days, clones were tested by a b-galactosidase filter assay. Among these, 360 were tested in a secondary screening. For this purpose the plasmid coding for each putative partner was extracted and used to transform E. coli strain B290 with electroporation. For each transformation 3 different colonies were analyzed and positive plasmids were re-transformed into EGY48 with pEG202-PRMT6; 179 clones were confirmed to be Leu+ and.
