Fig. 8: A model of tPARP1-mediated RNA Pol III ADP-ribosylation forms a positive feedback loop to facilitate apoptosis.
From: Truncated PARP1 mediates ADP-ribosylation of RNA polymerase III for apoptosis
Pol III mediates the activation of caspase 3 during the early stage of apoptosis. The early activation of caspase 3 digests a portion of PARP1. Cleaved PARP1 relocates from nucleus to cytoplasm to catalyze ADP-ribosylation on Pol III in cytoplasm, which in turn activates Pol III and RIG-I-dependent apoptotic pathways. ADP-ribosylated Pol III induces a positive feedback loop to further activate caspase 3 and PARP1 cleavage. Eventually, this positive feedback loop accelerates apoptosis. The green lines represent the initial activation of caspase 3, limited cleavage of PARP1, and early-phase activation of the RIG-I pathway. The red lines represent the positive feedback loop via ADP-ribosylation of Pol III, full activation of caspase 3, and the RIG-I pathway to accelerate apoptosis.
