Such dual roles in both telomere maintenance and transcriptional regulation have recently been ascribed to additional telomere-associated DNA-binding proteins, including TRF1 and TRF2 [48,49]. made of molecules that carried a novel non-telomeric consensus: 5-TNCANNAGKKKTTAGG-3 (where K=G/T and N=any foundation). Binding studies showed that these non-telomeric sites were made of an OB1-binding motif (TTAGG) and a non-telomeric motif (NT motif), with the two motifs identified by distinct regions of the OB1 website. POT1 interacted with these non-telomeric binding sites with high affinity and specificity, even when bound to its dimerization partner TPP1. This intrinsic ability of POT1 to recognize NT motifs increases the possibility that the protein may fulfill additional functions at particular non-telomeric locations of the genome, in perhaps gene transcription, replication, or restoration. transcription/translation inside a rabbit reticulocyte lysate. Flag-tagged version of full Mogroside VI length POT1 and each POT1 mutants were synthesized as directed from the pCMV1-Flag-POT1 vector (full size) and pcDNA3.1-Flag-POT1 vector series (aa 1-155, 1-340, 1-470), respectively. In a final volume of 50 l, one microgram of POT1 plasmid was transcribed/translated using the TnT? Quick Coupled system, according to the manufacturer’s instructions (Promega, Madison, WI). A water-programmed lysate (Mock) was produced in parallel to serve as a negative control. Aliquots of the reactions were analyzed by Western blotting using the anti-Flag M2 antibody (Physique 4B). Open in a separate window Physique 4 The NT motif is recognized by the OB1 domain name of POT1A) Schematic description of the Flag-POT1 mutants tested and summary of the results. B) Western blot analysis of the Flag-POT1 mutants. The translated mutants were detected using the anti-Flag M2 antibody. C) EMSA with the translated Flag-POT1 Mogroside VI mutants. Full length Flag-POT1 and its truncated mutants were incubated with the indicated radiolabeled probes (OB1/OB2, OB1, NT/OB1, and NT), after which protein/DNA complexes were resolved by electrophoresis. Migration of the Flag-POT1/DNA complex (arrowhead) was inversely proportional to the size the Flag-POT1 protein, with the Flag-POT1(1-155) protein migrating the fastest. 2.4. Flag-POT1 in extracts of transfected 293T cells 293T cells were cultivated in 5% CO2 at 37C in DMEM supplemented with 10% fetal bovine serum and 100 U/ml penicillin/streptomycin. Log growth cells were transiently transfected by the calcium phosphate method using MBS mammalian transfection kit (Stratagene, La Jolla, CA), following the manufacturer’s instructions. Cells were transiently transfected without plasmid (Mock) or with the pCMV1-Flag-POT1 vector (Flag-POT1). Forty-eight hours post-transfection, cells were harvested for preparation of whole cell extracts, as explained previously for the Shelterin complex [40]. 2.5. His-tagged human POT1(1-314) in extracts of E. coli cells Bacterial vector pET28a-POT1(1-314) expressing an His-tagged human POT1(1-314) was transformed into Rosetta2(DE3) cells (Novagen) following standard protocols. Cells were produced at 37C until reaching an OD600 of 0.5, after which cells were induced with 1 mM IPTG at 37C for 4 hours prior to harvesting. The cell pellet was lysed in buffer A (20 mM BICINE, 100 mM NaCl, 40 Mogroside VI mM imidazole, 2 mM -mercaptoethanol, pH 8.5) plus protease inhibitor cocktail (Sigma, #P8849) using three passes at 15,000-20,000 psi in an Emulsiflex C-5 (Avestin Inc., Ottawa, ON). The extract was cleared by centrifugation at 18,000 g for 30 minutes. The His-tagged POT1(1-314) protein was detected by Western blot using a nickel (Ni2+)-activated derivative of horseradish peroxidase, HisProbe-HRP (ThermoFisher Scientific, Waltham, MA). Detection was following the manufacturer’s MUC16 instructions, except that this blocking and binding actions were performed in the presence of 3M guanidine-HCl. 2.6. SELEX SELEX was performed as we have previously carried out [41], except for minor modifications. A 75-mer single-stranded (ss) oligonucleotide made up of a 35-nt random core flanked by PCR priming sequences (Physique 1A) was used as starting material. In the first round of selection, 5 g Mogroside VI of this randomized oligo (215 pmoles, 130 trillion molecules) was incubated with 5 l of rabbit reticulocyte lysate programmed with Flag-POT1 in a 20 l reaction made up of 1X binding buffer (4% glycerol, 1 mM MgCl2, 1 mM DTT, 50 mM NaCl, 10 mM Tris-HCl, pH 7.5). After 30 minutes at room heat, 10 l of magnetic beads coated with the anti-Flag M2 antibody were added. M450 Sheep anti-Mouse IgG beads coated with the M2 antibody were prepared as previously explained [40,42]. After an hour of rotation at 4C, the beads were washed 3 times with 500 l of ice-cold 1X binding buffer, after which the selected oligos were eluted at 95C for 5 minutes Mogroside VI in a 100 l of PCR mix. Re-amplification of the eluted molecules was.