MHC class I chain-related gene B promoter polymorphisms and celiac disease.

The possibility that susceptibility to celiac disease (CD) might be influenced by the MHC class I chain-related gene family, MICA and MICB, has been previously reported. In this study, we analyzed the MICB promoter and examined the association of the polymorphisms found within such in a group of CD patients. To study the MICB promoter we sequenced the 5' flanking region of MICB gene in DNA from homozygous B-lymphoblastoid cell lines corresponding to the most frequent MICB alleles found in our population (MICB*00502, MICB*002, MICB*004, and MICB*008). DNA from a MICB*003 homozygous individual was also analyzed. Sequence analysis revealed six single nucleotide polymorphisms located at positions 45860 C/A, 45862 G/C, 45877 C/G, 46113 A/C, 46219 G/C, and 46286 G/C and an insertion of 2 bp --/AG at position 45944 according to the published genomic sequence. Those polymorphisms were found to be associated in four different haplotypes corresponding to different MICB alleles. Subsequently, 126 CD subjects and 117 healthy controls were typed by polymerase chain reaction using sequence-specific primers for these polymorphisms. MICB promoter polymorphism haplotypes were also found in our population and showed strong linkage disequilibrium with MICB alleles. MICB promoter polymorphism Haplotype 3, included in MICB*002 and MICB*008 alleles, was found to be overrepresented in CD patients (79.4% CD patients vs 45.3% healthy controls; p(c) < 0.0001; OR = 4.64; CI 95% = 2.64-8.16). Both MICB*008 and MICB*002 alleles were found as part of the CD susceptibility extended haplotypes B8/DR3/DQ2, B18/DR3/DQ2, and DR4/DQ8.

Transcriptional regulation of ULBP1, a human ligand of the NKG2D receptor.

Tumor cells expressing ligands of the NKG2D receptor stimulate anti-tumor immunity mediated by natural killer and T cells. In humans, NKG2D ligands (NKG2DL) are encoded by MIC and ULBP proteins. NKG2DL exhibit highly restricted expression in healthy tissues but are widely expressed in tumors. However, regulation of each NKG2DL differs substantially in different cancer cells. In this study, we characterized the mechanisms that regulate the expression of ULBP1. We show that the transcription of ULBP1 strictly depends on the binding of Sp1 and Sp3 to a CRE(1) site located in the ULBP1 minimal promoter. The mutation or deletion of this Sp1/Sp3 binding site abolished the transcription of ULBP1. It also diminished the transactivation of ULBP1 promoter by Sp3 overexpression, but not by Sp1, indicating that Sp3 is the main transcription factor that regulates ULBP1 through the CRE(1) site. Experiments in SL2 cells showed that the ULBP1 promoter was inactive in the absence of the Sp proteins and indicate that Sp3 is the essential activator of ULBP1 transcription, because the overexpression of Sp3 up-regulated its promoter activity > 500-fold. Additionally, we demonstrated that AP-2alpha repressed the expression of ULBP1 in HeLa cells by interfering with the binding of Sp3 and Sp1 to the ULBP1 promoter. These data indicate that Sp1, Sp3, and AP-2alpha may play an important role in the immunosurveillance against cancer. Finally, the definition of ULBP1 regulation may have implications for development of new therapeutic strategies against cancer cells.