Abstract
Transactivation response element RNA-binding protein (TRBP or TARBP2) initially identified to play an important role in human immunodeficiency virus (HIV) replication also has emerged as a regulator of microRNA biogenesis. In addition, TRBP functions in signaling pathways by negatively regulating the interferon-induced double-stranded RNA (dsRNA)-activated protein kinase (PKR) during viral infections and cell stress. During cellular stress, PKR is activated and phosphorylates the α subunit of the eukaryotic translation factor eIF2, leading to the cessation of general protein synthesis. TRBP inhibits PKR activity by direct interaction as well as by binding to PKR’s two known activators, dsRNA and PACT, thus preventing their interaction with PKR. In this study, we demonstrate for the first time that TRBP is phosphorylated in response to oxidative stress and upon phosphorylation, inhibits PKR more efficiently promoting cell survival. These results establish that PKR regulation through stress-induced TRBP phosphorylation is an important mechanism ensuring cellular recovery and preventing apoptosis due to sustained PKR activation.
Highlights
The double-stranded RNA-activated protein kinase (PKR) is an interferon (IFN)-induced serine/threonine protein kinase expressed ubiquitously in mammalian cells[1,2,3]
To evaluate TAR RNA-binding protein (TRBP)’s effect on the cellular response to oxidative stress, we established a stable HeLa-Tet off cell line that would conditionally overexpress Flag-TRBP only when doxycycline was absent from the growth medium
The cells were expressing high level of Flag-TRBP when exposed to oxidative stress and this allowed us to assay the effect of TRBP overexpression on cellular apoptosis and PKR activation
Summary
The double-stranded RNA (dsRNA)-activated protein kinase (PKR) is an interferon (IFN)-induced serine/threonine protein kinase expressed ubiquitously in mammalian cells[1,2,3]. As the dsRBMs in PKR, PACT, and TRBP mediate protein-protein interactions[26], these three proteins form both heterodimers as well as homodimers and the stress-dependent phosphorylation of PACT changes the relative strengths of PKR-PACT, PACT-TRBP, and PACT-PACT interactions to bring about a timely and transient PKR activation with precise control[25,27]. This regulates the general kinetics as well as level of eIF2α phosphorylation thereby influencing the cellular response to stress either as recovery and survival or elimination by apoptosis[28]. Our findings implicate MAPKs (ERK1/2 and JNK) in oxidative stress-induced TRBP phosphorylation, and show that TRBP phosphorylation significantly enhances TRBP’s ability to interact with and inhibit PKR during oxidative stress to regulate apoptosis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
