FIG. 2.

Mapping of a major human IL-21R transcription initiation site by 5′ RACE. (A) Locations of primers used in the 5′ RACE. IL21R GSPs 1, 2, and 3 are complementary to the regions from +805 to +828, +647 to +670, or +607 to +630, respectively (relative to the boundary of IL-21R 5′ cDNA) (35). RACER 5′ primer and RACER 5′ nested primer complementary to the RACER RNA oligonucleotide were provided by the GeneRACER kit. (B) Total RNA was isolated from human PB T cells treated with 2 μg/ml of anti-CD3 plus 1 μg/ml of anti-CD28 antibody for 2 h. The 5′ end of IL-21R was PCR amplified by RACER 5′ primer with GSP1 (product 1) or GSP2 (product 2). The nested PCR was performed by using nested primers and PCR product 1 (lane 2) and product 2 (lane 3). Lane 1 shows the molecular weight marker. Arrows indicate the bands cut from the gel for subcloning and sequencing. (C) Partial sequence of the 5′ regulatory region of the IL21R gene showing the major transcription initiation site (arrow) 243 nucleotides 5′ of exon 1a (open box).