Transcription patterns from hIL-5R gene and minigenes.

(A) Northern blot hybridization experiments were performed using a probe that detects both membrane associated (TM) and soluble (SOL) IL-5Rα mRNA isoforms, using RNA from Cos-1 cells transfected with the pSV-MINI-1 or -2 constructs. In both cases, only IL-5Rα-TM was detected. Construct pSV-MINI-2 includes an SV40 polyadenylation sequence downstream of exon 11, ruling out the possibility that the absence of the SOL mRNA is due to a deficiency in recognizing the SOL transcript-specific polyadenylation signal. The size and location of the TM-specific transcript is indicated. (B and C) Competitive RT-PCR analysis and Northern analysis of IL-5Rα transcripts from FDC-P1-MINI-1.1 cells grown in EL4-conditioned medium (lanes CM, a source of murine IL-3), or rhIL-5 (lanes IL-5) for 2 weeks, or in rhIL-5 for 2 weeks followed by EL-4-conditioned medium for a further 7 days (lanes IL-5/CM). Representative of 3 independent experiments. (D) Culture in rhIL-5 induces high-affinity IL-5 binding sites on FDC-P1-MINI-1.1 cells. Human IL-5 was radiolabeled using¹²⁵I by the iodogen procedure and Scatchard plot analysis was performed. No binding was detected to cells grown in EL-4 conditioned medium alone.