Human ADAM 33 mRNA expression profile and post - transcriptional regulation

Running Title : ADAM33 mRNA profile and postranscriptional effect of 3'UTR Abstract We examined transcript expression and post-transcriptional regulation of human ADAM33, a recently identified asthma gene. A detailed mRNA expression profile was obtained using Northern, RT-PCR and ISH analyses. ADAM33 mRNA was expressed significantly in smooth muscle-containing organs, minimally in immune organs and hematopoietic cells and highly in repairing duodenal granulation tissue. Expression was seen in asthmatic subepithelial fibroblasts and smooth muscle but not in respiratory epithelium. In all tissues, transcripts of ~ 5 kb predominated over those of ~3.5 kb by 2-to 5-fold. The effect of the 3'UTR on ADAM33 protein expression and maturation was examined. The presence of the 3'UTR in untagged full-length constructs promoted prodomain removal, detected as mature ~100 kD protein by ADAM33-reactive antibodies; in its absence, maturation was 2-to 3-fold less in HEK293 cells. His-tagged and untagged constructs lacking the 3'UTR demonstrated that lack of maturation was not via tag-mediated effects. Minimal maturation of ADAM33 occurred in primary lung and MRC5 fibroblasts following adenoviral-mediated expression of ADAM33 lacking the 3'UTR. In contrast, prodomain removal was observed with plasmids and adenovirus encoding only the pro-and catalytic domains. Thus, the 3'UTR of ADAM33 and domains downstream of the catalytic regulate potential ADAM33 activity. Mechanisms of regulation of ADAM33, distinct from closely related ADAMs, thus include mRNA localization and processing and protein maturation.