Characterization of a novel positive transcription regulatory element that differentially regulates the alpha-2-macroglobulin gene in replicative senescence.

Alpha-2-macroglobulin (α2M), a protease inhibitor, is implicated in Alzheimer's disease, atherosclerosis, and other age-related diseases. The elevated level of α2M mRNA has been described in replicative senescence and it could be used as a biomarker of the aging cells. However, the mechanism responsible for the up-regulation of its expression is still unclear. This report identified a novel transcriptional regulatory element, the α2M transcription enhancement element (ATEE), within the α2M promoter. This element differentially activates α2M expression in senescent versus young fibroblasts. Electrophoretic mobility shift assays revealed abundant complexes in senescent cell nuclear extracts compared with young cell nuclear extracts. The DNase I footprint revealed the protein-binding core sequence through which the protein binds the ATEE. Mutation within ATEE selectively abolished α2M promoter activity in senescent (but not young) cells. These results indicated the ATEE, as a positive transcription regulatory element, contributes to the up-regulation of α2M during replicative senescence.