The mitogen-induced increase in T cell size involves PKC and NFAT activation of Rel/NF-kappaB-dependent c-myc expression.

Cell growth during the G1 stage of the cell cycle is partly controlled by inducing c-myc expression, which in B cells is regulated by the NF-kappaB1 and c-Rel transcription factors. Here, we show that c-myc-dependent growth during T cell activation requires c-Rel and RelA and that blocking this growth by inhibiting protein kinase C theta (PKCtheta) coincides with a failure to upregulate c-myc due to impaired RelA nuclear import and inhibition of NFAT-dependent c-rel transcription. These results demonstrate that different Rel/NF-kappaB dimers regulate the mitogenic growth of mature T and B cells, with a signaling pathway incorporating PKCtheta and NFAT controlling c-Rel/RelA-induced c-myc expression in activated T cells.