Interferon-γ activates expression of p15 and p16 regardless of 9p21.3 coronary artery disease risk genotype

Abstract

Objectives: Because post-transcriptional mechanisms modulate levels of p16 (encoded by CDKN2A) and p15 (encoded by CDKN2B), we tested whether interferon-γ regulates the expression of these proteins and the effect of the 9p21 genotype. Background: The mechanism whereby the common variant at chromosome 9p21.3 confers risk for coronary artery disease (CAD) remains uncertain. A recent report proposed that 9p21.3 confers differential activation of adjacent genes in response to interferon-γ, and reported that mRNA levels of CDKN2B are reduced in response to interferon-γ. Methods: Human umbilical vein endothelial cells (HUVECs), aortic smooth muscle cells, HeLa cells, HEK293 cells, and 16 human lymphoblastoid cell lines, all genotyped for the 9p21.3 locus, were treated with interferon-γ and analyzed by immunoblot. Results: In all cells tested - except HUVECs where expression was not modulated by interferon-γ - regardless of 9p21.3 genotype, interferon-γ increased the expression of p16 and p15. Northern blot analysis confirmed that interferon-γ has little effect on mRNA levels of CDKN2A and CDKN2B. Conclusions: The 9p21.3 risk genotype does not affect the activation of cyclin-dependent kinase inhibitors p15 and p16 by interferon-γ. Thus, another mechanism is likely to account for the CAD risk associated with this locus. © 2013 American College of Cardiology Foundation.