Transcriptomic effects of caspase cleavage at TFIIB residue D207 during apoptosis and KSHV infection [TFIIB(D207A)]
Cellular stressors often cause widespread repression of RNA polymerase II (RNAP II) activity, which is thought to facilitate a focused transcriptional output towards stress resolution. In many cases, however, the underlying regulatory mechanisms remain unknown. Here, we demonstrate that stress-induced downregulation of the general transcription factor TFIIB tempers expression of specific stimulus response genes. Following a variety of stressors, TFIIB is proteolytically cleaved between its cyclin folds at conserved aspartic acid residue D207 by caspases- 3 and 7. Cleavage in this portion of the protein significantly reduces the ability of TFIIB to form a TBP-TFIIB-DNA promoter complex in vitro. Using both overexpression and endogenous base-editing, we find that B and T cells that are unable to cleave TFIIB upregulate expression of a select gene set during apoptosis. These TFIIB-sensitive genes are primarily short, stimulus-responsive and proto-oncogenic loci, and cleavage of TFIIB temporally restricts their expression. Failure to cleave TFIIB during stress leads to aberrant lymphocyte proliferation during chemical perturbation. Hence, caspase targeting of TFIIB destabilizes transcription to tune gene expression, allowing for proper stress resolution. Overall design: The effects of caspase-driven TFIIB depletion on gene expression during apoptosis and lytic KSHV infection were assessed by comparing cells exogenously overexpressing TFIIB-2xStrep ("WT") or caspase-resistant TFIIB(D207A)-2xStrep ("D207A"). Cells were mock treated, treated with the extrinsic apoptosis inducer TRAIL, or treated with doxycycline ("DOX") to initiate lytic viral infection for 24 or 48 hours. This was followed by RNA-seq and differential gene expression analysis.