3 using T7 RNA polymerase and an SP6/T7 in vitro transcription kit (Roche, Nutley, NJ).16 Transcripts were purified using native polyacrylamide gel electrophoresis.16 RNA oligonucleotides (Invitrogen,

Carlsbad, CA) were 3′-end labeled with 32P using Ambion’s protocol (Austin, TX). Unincorporated label was removed using a NucAway spin column (Ambion). IEC-6 and Caco-2 cells (5 × 106) were untreated or transfected with 30 μg of a wt HuR plasmid construct pcDNA3.1/mHuRcoding-3′UTR/Flag or 10 μM of siHuR or control siRNA for 48 hours prior to harvesting for homogenate preparation. For developmental studies, rat ileal epithelium and kidney cells were derived from 1- and 4-week-old Sprague-Dawley learn more rats (Taconic, Hudson, NY). The terminal ileum was defined as the distal 30% of the length of the small bowel. Tissues were homogenized with an Omni-Mixer homogenizer (Omni International, Kennesaw, GA) before protein extraction. Cellular and tissue homogenates were prepared by four cycling of freezing and thawing of cells in a lysis buffer containing 20 mM Tris (pH 7.5), 150 mM NaCl, 1 mM Na2EDTA, 1 mM EGTA, 1% Triton, 2.5 mM sodium pyrophosphate, 1 mM beta-glycerophosphate, 1 mM Na3VO4, 1 μg/mL leupeptin, and 1 mM PMSF, with the latter added immediately before use. The supernatant containing protein homogenate was obtained by centrifugation at 16,000g for 15 minutes BMS-354825 concentration at 4°C. Twenty

micrograms of IEC-6 cytoplasmic protein were incubated with 2 × 104 cpm of 32P-labeled transcript for 30 minutes at 37°C, followed by treatments to minimize nonspecific protein bindings as described.18 Samples were electrophoresed in 7% native polyacrylamide gel with 0.5× TBE (Tries borate-EDTA) running buffer. Dried

gels were exposed to film at −80°C for 24 hours. Fifty micrograms of IEC-6 or Caco-2 proteins were electrophoresed in 12% polyacrylamide gels and analyzed by western blotting.18 Membranes were stripped with Restore Western Blot Stripping Buffer (Bio-Rad) for sequential probing. Animals were housed, fed, and handled according to the National Institutes of Health (NIH) Guide for the Care and Use of Laboratory Animals and under a protocol approved by Institutional Animal Care Ponatinib mouse and Use Committee of the University of Pittsburgh. Statistical analysis was performed using In-Stat software (GraphPad Software, San Diego, CA). Unless otherwise stated, means were compared using the Tukey-Kramer multiple comparisons test, all values were mean ± standard deviation (SD), and a value of P < 0.05 was considered statistically significant. The 3′UTR was divided based on convenient restriction sites to begin to dissect out the relevant cis-elements. Three different sized fragments of the 3′UTR were incorporated into two different reporter constructs, one for rapid assessment on reporter protein expression (rASBT3′-luciferase) and one for kinetic analysis of mRNA half-life (rASBT3′-βglobin) (Fig. 1).