Abstract Signals mediated by autocrine activation of the human-specific complement receptor CD46 during T cell receptor (TCR) stimulation are vital to Th1 induction in human CD4+ T cells, but how exactly CD46 in a molecular level mediates this role is currently undefined. CD46 is expressed in different isoforms that can bear either one of two distinct cytoplasmic tails: CYT-1 or CYT-2. Nuclear translocation of CYT-1 is a critical requirement for the expression of genes coding for nutrient-influx-channels and mTORC1 activity that mediate metabolic adaptations needed for Th1 responses. The lack of a DNA binding domain in CD46-CYT-1 precludes it from acting directly as a transcription factor (TF) and we hence hypothesized that CYT-1 regulates gene expression via direct interaction with specific TF activator and/or repressor complexes. Indeed, CUT&RUN experiments performed using our novel antibody raised against cleaved CYT-1 identified key members of the KLF/SP TFs gene family as potential interacting partners of CD46-CYT-1. Subsequent ELISA and MST experiment confirmed strong, dose-dependent CYT-1/KLF/SP TFs interactions and also demonstrated that CYT-1 fostered KLF/SP TFs binding to appropriate DNA motifs. Genome-wide comparison of the KLF/SP TFs and CYT1 bound genes in T cells revealed their enrichment in crucial basic cell-physiological pathways. Moreover, the CUT&RUN data in conjunction with ATAC-seq analyses indicated that this novel CYT-1/KLF/SP axis may control general chromatin remodeling – a notion we are currently exploring. These data define a novel and critical human-specific pathway of gene regulation and further underpin the vital role of intracellular/autocrine complement in the regulation of normal cellular activity.