Characterization Of a Weakly Expressed KIR2DL1 Allele

The variegated expression of the human KIR family of class I MHC receptors provides an interesting model system for the study of stochastic activation of gene transcription. Previous studies have linked distal KIR promoter transcription to the initiation of KIR expression from the proximal promoter. In order to identify novel genetic alterations associated with decreased KIR expression, a group of 182 donors was characterized for KIR gene content, KIR transcripts, and FACS analysis of KIR surface expression. An individual was discovered that possessed a single copy of the KIR2DL1 gene but had a low level of gene expression by either FACS or Q-PCR.  Complete sequencing of the KIR2DL1 gene confirmed the presence of an intact coding region. Analysis of promoter elements revealed a cluster of three single nucleotide polymorphisms (SNPs) in the distal promoter approximately 1 kb upstream from the start of KIR2DL1 translation. These SNPs are also found in the distal promoter region of the non-transcribed KIR2DL5*002 allele as well as the KIR3DP1 pseudogene. One of these SNPs creates a functional binding site for the ZEB1 transcription factor.  Individuals possessing the ZEB1 site in their KIR2DL1 promoter produce high levels of a non-translatable distal KIR2DL1transcript that inhibits transcription from the proximal promoter, resulting in weak expression of this allele.

This research was supported in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research. Funded by NCI Contract HHSN261200800001E.