The transcription factor TRF2 has a unique function in regulating cell cycle and apoptosis

TLDR: It is shown that TRF2 knockdown results in increased expression of distinct pro-apoptotic genes and induces apoptosis, uncovering a critical and unanticipated role of a general transcription factor as a key regulator of cell cycle and apoptosis.

Abstract: Background Diverse biological processes and transcriptional programs are regulated by RNA polymerase II (Pol II), which is recruited by the general transcription machinery to the core promoter to initiate transcription. TRF2 (TATA-box-binding protein-related factor 2) is an evolutionarily conserved general transcription factor that is essential for embryonic development of Drosophila melanogaster, C. elegans, zebrafish and Xenopus. Nevertheless, the cellular processes that are regulated by TRF2 are largely underexplored. Results Here, using Drosophila Schneider cells as a model, we discovered that TRF2 regulates apoptosis and cell cycle progression. We show that TRF2 knockdown results in increased expression of distinct pro-apoptotic genes and induces apoptosis. Using flow cytometry, high-throughput microscopy and advanced imaging-flow cytometry, we demonstrate that TRF2 regulates cell cycle progression and exerts distinct effects on G1 and specific mitotic phases. RNA-seq analysis revealed that TRF2 controls the expression of Cyclin E and the mitotic cyclins, Cyclin A, Cyclin B and Cyclin B3, but not Cyclin D or Cyclin C. To identify proteins that could account for the observed regulation of these cyclin genes, we searched for TRF2-interacting proteins. Interestingly, mass spectrometry analysis of TRF2-containing complexes identified GFZF, a nuclear glutathione S-transferase implicated in cell cycle regulation, and Motif 1 binding protein (M1BP). TRF2 has previously been shown to interact with M1BP and M1BP has been shown to interact with GFZF. Furthermore, available ChIP-exo data revealed that TRF2, GFZF and M1BP co-occupy the promoters of TRF2-regulated genes. Using RNAi to knockdown the expression of either M1BP, GFZF, TRF2 or their combinations, we demonstrate that although GFZF and M1BP interact with TRF2, it is TRF2, rather than GFZF or M1BP, that is the main factor regulating the expression of Cyclin E and the mitotic cyclins. Conclusions Our findings uncover a critical and unanticipated role of a general transcription factor as a key regulator of cell cycle and apoptosis.