The Δ133p53 Isoform Reduces Wtp53-induced Stimulation of DNA Pol γ Activity in the Presence and Absence of D4T.

Dexi Chen,Kai Liu,Jiming Yin,Lijun Pang,Xianghua Guo,Yunjin Zang,Feili Wei

doi:10.14336/ad.2016.0910

Abstract

The mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is due to the inhibition of mitochondrial DNA (mtDNA) polymerase γ (pol γ). Previous studies have shown that wild type p53 (wtp53) can interact with pol γ and mtDNA to enhance mitochondrial DNA base excision repair (mtBER) activity and increase the accuracy of DNA synthesis. The N-terminal transactivation domain and central specific DNA-binding domain of p53 play critical roles in the stimulation of BER. In this study, we identified the possible roles of wtp53, Δ40p53 and Δ133p53 in regulating mtDNA pol γ activity in cells with d4T treatment. The results show that Δ40p53 and Δ133p53 can exist in mitochondrial fragments and form polymers with themselves or wtp53. Unlike wtP53, Δ133p53 alone cannot increase DNA pol γ activity. More importantly, we found that Δ133p53 played a negative role in p53 stimulation of DNA pol γ activity when studied in d4T-treated and d4T-untreated mitochondrial extracts. Gel shift data also indicate that Δ40p53 and Δ133p53 cannot interact with APE. Wtp53 and Δ40p53 can act antagonize the effect of d4T inhibition of DNA pol γ activity. However, when wtp53 interacted with Δ133p53, DNA pol γ activity was significantly decreased. Conclusion: Δ133p53 negatively regulates p53’s stimulation of pol γ in the presence and absence of d4T.

Highlights

The mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is due to the inhibition of mitochondrial DNA polymerase γ
We examined the effect of wtp53, Δ40p53 and Δ133p53 on mitochondrial DNA base excision repair (mtBER) using an in vitro nucleotide incorporation assay and report that Δ133p53 alone cannot increase DNA pol γ activity, it can reduce the DNA pol γ activity induced by p53 in both d4Ttreated and d4T-untreated mitochondria
Previous studies have shown that p53 can affect the stability of mitochondrial DNA. p53 isoforms have recently been discovered in different tumor cell lines and tumor tissues, which may play a role in the development of tumors [27, 36, 37]

Summary

Introduction

The mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is due to the inhibition of mitochondrial DNA (mtDNA) polymerase γ (pol γ). Δ133p53 decreases DNA pol γ activity by inhibiting wtP53 polymerase unique to the mitochondria and is involved in the replication of mtDNA as well as mtBER [13,14,15]; the mitochondrial toxicity of d4T is caused by the dysfunction of these processes. Previous studies have shown that wildtype p53 (wtp53) can combine with mtDNA and pol γ to enhance mtBER activity and maintain mitochondrial genetic stability [22,23,24]. The N-terminal transactivation domain and central DNA-binding domain of p53 play a critical role in stimulating BER and Δ40p53 has a major influence over p53 activity by controlling p53 ubiquitination and cell localization [29, 30]

Methods

Results

Conclusion