Genetic Variation at a Yin-Yang 1 Response Site Regulates the Transcription of Cyclin-Dependent Kinase Inhibitor p18 INK4C Transcript in Lupus-Prone Mice

• Published in: The Journal of immunology (1950) Vol. 188; no. 10; pp. 4992 - 5002
• Main Authors: Potula, Hari-Hara S. K., Morel, Laurence
• Format: Journal Article
• Language: English
• Published: 15.05.2012
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.1101992

Abstract We have previously shown that a novel −74 C-to-T mutation in the promoter of the cyclin-dependent kinase inhibitor p18Ink4c (p18) gene was associated with a reduced p18 expression in B cells from mice carrying the Sle2c1 lupus susceptibility locus. To determine the function of the −74 C/T single nucleotide polymorphism, we have characterized the proximal promoter of the mouse p18 gene. Functional analysis of the 5′ flanking region by sequential deletions revealed crucial elements between −300 and +1, confirming the in silico prediction that the −74 T allele created a novel Yin-Yang 1 (YY-1) binding site adjacent to an existing one common to both alleles. Moreover, we found that YY-1, E2F1, and Sp-1 can synergistically enhance the activity of the p18 promoter. Mutational inactivation revealed that YY-1 binding regulates the p18 activity in an allele-dependent fashion. EMSAs with splenic B cell extracts directly demonstrated that YY-1 binds to the p18 promoter with differences between the C and the T alleles. We also determined in vivo by chromatin immunoprecipitation that the T allele resulted in increased YY-1 and decreased Nrf-2 binding to the p18 promoter as compared with the C allele in B cells. Thus, YY-1 is a direct regulator of p18 gene expression in an allele-dependent fashion that is consistent with the lupus-associated T allele, inducing a lower p18 transcriptional activity by increasing YY-1 binding. These results establish the p18 −74 C/T mutation as the leading causal variant for the B1a cell expansion that characterizes the NZB and NZM2410 lupus-prone strains.