Gene dosage and down-regulation of the alpha-interferon receptor

The gene coding for the alpha,beta-interferon (alpha,beta-IFN) receptor is localized to chromosome 21. Cells from patients with Down's syndrome (trisomy 21) contain an extra chromosome 21, which results in a 1.5 times increase of dosage for the genes localized to this chromosome. Trisomy 21 cells express more cell-surface alpha-IFN receptors, consistent with the increased gene dosage. Down-regulation of the alpha-IFN receptors in trisomy 21 and normal cells was studied by incubating the cells with alpha-IFN. The alpha-IFN-induced effects showed 1.6 times more internalized cell-surface alpha-IFN receptors in trisomy 21 cells compared with normal cells, but no statistically significant change in the dissociation constants. A close relationship was found between the alpha-IFN receptor number and the biological response expressed as 2',5'-oligoadenylate synthetase activity.