N6-Methyladenosine Directly Regulates CD40L Expression In CD4+ T Lymphocytes

<strong>Abstract</strong> T cell activation is a highly regulated process, modulated via the expression of various immune regulatory proteins including cytokines, surface receptors and co-stimulatory proteins. N⁶-methyladenosine (m⁶A) is an RNA modification that can directly regulate RNA expression levels and it is associated with various biological processes. However, the function of m⁶A in T cell activation remains incompletely understood. We identify m⁶A as a novel regulator of the expression of CD40 ligand (CD40L) in human CD4⁺ lymphocytes. Manipulation of the m⁶A ‘eraser’ fat mass and obesity-associated protein (FTO) and m⁶A ‘writer’ protein methyltransferase-like 3 (METTL3) directly affects the expression of CD40L. The m⁶A ‘reader’ protein YT521-B homology domain family-2 (YTHDF2) is able to recognize and bind m⁶A specific sequences on the <em>CD40L</em> mRNA and promotes its degradation. This study demonstrates that CD40L expression in human primary CD4⁺ T lymphocytes is regulated via m⁶A modifications, elucidating a new regulatory mechanism in CD4⁺ T cell activation that could possibly be leveraged in the future to modulate T cell responses in patients with immune-related diseases. <strong>Data deposited</strong> meRIP sequencing: read counts of healthy control peripheral blood-derived CD4+ T lymphocytes (figure 1 in article). meRIP sequencing: per gene TMM normalized log2(CPM + 0.168) expression values of healthy control peripheral blood-derived CD4+ T lymphocytes (figure 1 in article). Also includes Log2FoldChange values or each gene.