DIFFERENT BINDING OF NF-Y TRANSCRIPTIONAL FACTOR TO DQA1 PROMOTER VARIANTS

Polymorphism in the HLA-DQA1 promoter (QAP) sequences could influence the gene expression through a differential binding of transcriptional factors. Considering the main role played by the Y-box in the transcri ption, we focused on the QAP4 variants differing for a G vs A transiti on from the QAP Y-box consensus sequence. Electrophoretic Mobility Shi ft Assay using the two Y-box sequences was performed ro determine whet her this mutation could be reflected in an allele-specific binding of transcriptional factors. Indeed, the NF-Y specific band, recognised by supershift experiments, was clearly observed using the Y-box consensu s probe but it was barely detectable with the QAP4 one. On the contrar y, two other complexes were found eo more strongly interact with QAP4 Y-box in comparison to the consensus sequence. The analysis of a selec ted panel of HLA homozygous lymphoblastoid cell lines by competitive R T-PCR and by Northern blotting revealed that the DQA1 0401, *0501, *0 601 alleles regulated by the QAP4 promoters were less expressed at the mRNA level than the DQA1 0201 allele regulated by the QAP2.1 variant . In conclusion, these results show an evident reduction of NF-Y bindi ng to the mutated QAP4 Y-box and a decreased mRNA accumulation of the DQA1 alleles regulated by these variants. Human Immunology, 59, 758-76 7 (1998). (C) American Society for Histocompatibility and Immunogeneti cs, 1998. Published by Elsevier Science Inc.