Mechanism of regulation of SATB1 during T helper cell differentiation

Abstract

SATB1 is a chromatin organizer protein enriched in T cells. It plays a crucial role in differentiation of naïve CD4+ T cells. Transcriptome analysis performed in our laboratory suggested that multiple promoters are involved in SATB1 expression (P1, P2, and P3) in mouse and human. Specifically, P2 promoter is increased in expression upon differentiation of CD4+ T cells into Th2 phenotype. Interestingly, expression of P1 promoter increased and P3 decreased upon activation of TCR signaling alone. We extended these observations to an in vitro system, the Jurkat cell line. Our finding in Jurkat cells suggests that different transcription factors downstream of TCR signaling and cytokine signaling may play a role in the regulation of SATB1 expression. We previously showed the involvement of STAT family of transcription factors in the regulation of P2 promoter expression. Here we show the role of NF-κB in the regulation of SATB1 P3 promoter expression by chemical inhibition of NF-κB in Jurkat cells subjected to polarizing conditions. However, upon NF-κB inhibitor treatment no significant effect was observed on SATB1 P1 promoter. We speculate AP1 family transcription factor FOS may regulate SATB1 P1 promoter. Preliminary data showed that STAT6 plays a crucial role in SATB1 P2 promoter expression upon cytokine signaling activation. Motif analysis and overlaying on genome show STAT6 binding to the upstream putative enhancer. Hence, we perform a chromosome conformation capture (3C) assay to study this promoter-enhancer interaction. So far, we have successfully standardized 3C assay. This study shows an interplay of direct effector transcription factors of TCR and cytokine signaling in SATB1 alternative promoter expression.