CD8 T lymphocytes deploy embryonic cell cycle control mechanisms for rapid cell proliferation.

Rapid proliferation of CD8 T cells is crucial for adaptive immunity against viral infection. CD8 T cells can complete division cycles in less than 6 h, representing a physiological extreme for somatic mammalian cells. Embryonic stem cells utilize specialized cell cycle control mechanisms, including subdued periodic expression, for rapid cell division cycles. CD8 T cell cycle control remains poorly understood. Here, we test whether CD8 T cells utilize embryonic mechanisms to promote rapid cell cycles. We comprehensively measure protein abundances in G1, S, and G2&M phases in three murine cell types: CD8 T cells, embryonic stem cells, and fibroblasts. We discover striking similarities between mESC and CD8 T cells. We demonstrate that CD8 T cells express Cyclin E1 and Emi1/Fbxo5 at high levels to promote S-phase entry. Interestingly, CD8 T cells and mESCs differ in the frequency of G2&M phase cells, the abundance of DNA replication origin licensing and initiation factors, and the abundance of APC/C substrates. Thus, somatic T cells have both unique and shared cell cycle control mechanisms to promote rapid cell cycles.