FIG. 7.

SBP2 expression increases selenoprotein mRNA and protein levels. (A) mRNA levels for the 15-kDa selenoprotein (sel 15), GPX1, and selenoprotein P (sel P) in HepG2 and HEK-293 cells were assessed by spotted array hybridization and PhosphorImager quantitation. All mRNA levels were normalized to GAPDH mRNA, and hybridizations were performed at least in triplicate. (B) mRNA levels for GPX1 and selenoprotein P (sel P) were assessed in HEK-293 cells by quantitative real-time reverse transcriptase PCR following transient transfection of the indicated SBP2 expression constructs. Note that transient transfection is not highly efficient; thus, increases in mRNA levels in the presence of SBP2 likely reflect a fraction of the total cell population. Means were compared using Student's t test; P was <0.01 for all samples. (C) Selenoproteins were labeled with sodium [⁷⁵Se]selenite following transfection of the indicated SBP2 constructs and analyzed by SDS-polyacrylamide gel electrophoresis and autoradiography. (D) Densitometric quantitation of the four prominent selenium-labeled bands shown in panel C, numbered from top to bottom of the gel. Means from two labeling experiments that were derived from independent transfections are given.