Runx/CBFβ transcription factor complexes regulate Ccl5 expression through two novel enhancers to enhance tumor immunity [dataset 2]

CCL5 (also known as RANTES) was originally known to be important to recruit memory T cells to infected sites, but it received much attention as an inhibitor to HIV’s entry into T lymphocytes of AIDS patients. Recently, it has been reported to be necessary to sustain Trm (Tissue-resident memory) T cells at local tissues as well as to play roles in manipulating tumor microenvironment by both host immunity and cancer cells. Nonetheless, little is known how Ccl5 expression is regulated, thus making it quite difficult for therapeutic intervention. Our study reveals that Runx/CBFβ transcription factor complexes antagonizes Ccl5 expression through two novel transcriptional enhancers. The proximal enhancer is required for the homeostatic expression of Ccl5 during the steady state, meanwhile the distal enhancer is necessary for the expression Ccl5 during the activated stage. We employed enChIP-seq to identify the distal enhancer located 1.35 Mb away from the promoter. This long distance interaction requires the help from Satb1, a global chromatin organizer. Our study reveals that the reduced amounts of Ccl5 by the deletion of the proximal enhancer results in an enhancement of metastasis in B16-F10 melanoma model. On the other hand, a Runx3-mutant mouse line in which Ccl5 expression is increased showed the opposite outcome, suggesting a novel inverse correlation between host Ccl5 levels and metastasis rate. Identification of DNA regions associated with CBFb on CD4+ and CD8+ T cells by ChIP-seq.