The tumor suppressor Ikaros engages the VPAC1 promoter in activated HuT 78 cells

Abstract

DNA sequence specific recruitment of transcription factors to gene promoters is essential for normal gene expression. Total Ikaros (IK) protein and its phosphorylation pattern change during activation of lymphocytes, altering its subnuclear localization and DNA binding. IK has been shown to decrease expression of an anti‐proliferative, G‐protein coupled receptor, vasoactive intestinal peptide receptor 1 (VPAC1) when ectopically overexpressed in NIH‐3T3 cells. The VPAC1 promoter contains 24 putative binding sites for IK, including four high affinity motifs. VPAC1 mRNA levels are dependent on the activation status of CD4 T cells, as TCR signaling downregulates VPAC1 expression. IK is hypothesized to engage the VPAC1 promoter upon activation and downregulate expression. Binding of IK to the VPAC1 promoter was queried using chromatin immunoprecipitation (ChIP). IK was enriched at the VPAC1 promoter in an activation (PMA/ionomycin) dependent manner in HuT 78 cells. Surprisingly, HuT 78 activation did not decrease VPAC1 mRNA. Future studies will overexpress DNA binding, non DNA binding, and alanine/aspartate mutant IK isoforms to determine their effect on IK binding. Engagement of the master regulator or lymphopoesis, IK, at the neuropeptide receptor VPAC1 promoter strengthens the neuroimmunomodulation connection at the molecular level.