PCIF1 is expressed in pancreatic β cells and represses insulin promoter activity in MIN6 cells. (A) Real-time PCR detection of PCIF1 reveals high expression in total pancreatic RNA. Total RNA from adult mouse tissues was isolated, and PCIF1 mRNA was quantitated by RT and real-time PCR detection. Data are normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels. The lowest expression, that for small intestine, was set to 1 for n-fold expression calculations. kid, kidney; intes, intestine; panc, pancreas; stom, stomach. (B) Immunohistochemistry of paraffin-embedded sections of adult mouse pancreas stained with anti-PCIF1. (C) Double immunofluorescence of fixed frozen sections of adult mouse pancreas for PCIF1 and insulin. (D) The insulin promoter reporters rat INS1 CAT and rat INS2 CAT were transfected into MIN6 cells in the presence of various amounts of PCIF1 expression vector (0, 250, and 500 ng). Data are normalized to internal-control β-galactosidase activity, and repression is expressed relative to 0 ng of PCIF1. *, P < 0.05; **, P < 0.005.