Allele-dependent transcriptional regulation of the human integrin α2 gene

Genetically controlled variation in alpha (2)beta (1) expression by human blood platelets was previously described. Sixty-two haplotype sequences corresponding to the proximal 5' regulatory region (-1096 to +1) of the alpha (2) gene were compared, and a dimorphic sequence -52C>T was identified that is located precisely between 2 tandem Sp1/Sp3 binding elements previously shown to be absolutely required for transcriptional activity of this gene in epithelial cell lines and the erythroleukemic cell line K562, The gene frequency of -52T in a random Caucasian population is approximately 0.35, and the expression of -52T correlates directly with reduced densities of platelet alpha (2)beta (1) In mobility shift analyses, the -52T substitution attenuates complex formation with both Sp1 and Sp3, When transfected into the erythroleukemia cell line Dami, promoter-luciferase constructs bearing the -52T sequence exhibit a 5-fold decrease in activity relative to the -52C construct, In transfected CHRF-288-11 megakaryocytic cells, the corresponding activity decreases by 10-fold, The -52T sequence appears to be in linkage disequilibrium with the previously defined allele A3 (807C; HPA-5b), known to be associated with diminished expression of platelet alpha (2)beta (1) In summary, a natural dimorphism has been identified within the proximal 5' regulatory region of the human integrin alpha (2) gene that is responsible for decreased expression levels of the integrin alpha (2)beta (1) on blood platelets through a mechanism that is probably mediated by the nuclear regulatory proteins Sp1 and Sp3.(Blood. 2001; 97:1721-1726) (C) 2001 by The American Society of Hematology.