Alternatively processed human E-selectin transcripts linked to chronic expression of E-selectin in vivo.

Abstract

E-selectin, also known as endothelial leukocyte adhesion molecule-1 (ELAM-1), is transiently expressed on endothelial cells in response to inflammatory cytokines such as IL-1 and TNF-alpha and mediates adhesion of leukocytes. The genomic structure of E-selectin is highly conserved and includes multiple polyadenylation signals and a number of AUUUA transcript destabilizing elements within the 3'-untranslated region (UTR). Anchored-PCR analysis indicates that all three polyadenylation signals within the human E-selectin 3'-UTR are indeed functional, and three forms of E-selectin transcripts (Types I, II, and III) generated by differential usage of these polyadenylation signals were detected in both cytokine-stimulated primary human endothelial cells and human skin tissue cultures. Although the longest transcript (Type III) is the most abundant form found in cytokine-stimulated human endothelial cells and human skin tissue cultures in vitro, only the shortest transcript (Type I) is detected in human dermal biopsies expressing cell surface E-selectin. Interestingly, the Type I E-selectin transcript lacks six of the mRNA destabilizing elements that are thought to mediate rapid degradation of the corresponding mRNA. In agreement with the absence of these mRNA decay signals, we determined that the Type I E-selectin transcript is more stable than the full-length Type III E-selectin transcript in an in vitro chimeric mRNA stability assay. Therefore, the presence of only the Type I transcript in skin biopsies of chronic inflammatory lesions suggests that differential polyadenylation of E-selectin transcripts may provide the molecular basis for the observed chronic expression of E-selectin in human dermal disorders.