The lyase activity of the DNA repair protein β-polymerase protects from DNA-damage-induced cytotoxicity

Abstract

Small DNA lesions such as oxidized or alkylated bases are repaired by the base excision repair (BER) pathway. BER includes removal of the damaged base by a lesion-specific DNA glycosylase, strand scission by apurinic/apyrimidinic endonuclease, DNA resynthesis and ligation. BER may be further subdivided into DNA beta-polymerase (beta-pol)-dependent single-nucleotide repair and beta-pol-dependent or -independent long patch repair subpathways. Two important enzymatic steps in mammalian single-nucleotide BER are contributed by beta-pol: DNA resynthesis of the repair patch and lyase removal of 5'-deoxyribose phosphate (dRP). Fibroblasts from beta-pol null mice are hypersensitive to mono-functional DNA-methylating agents, resulting in increases in chromosomal damage, apoptosis and necrotic cell death. Here we show that only the dRP lyase activity of beta-pol is required to reverse methylating agent hypersensitivity in beta-pol null cells. These results indicate that removal of the dRP group is a pivotal step in BER in vivo. Persistence of the dRP moiety in DNA results in the hypersensitivity phenotype of beta-pol null cells and may signal downstream events such as apoptosis and necrotic cell death.

A unified view of base excision repair: Lesion-dependent protein complexes regulated by post-translational modification

“…This mechanism or process of complex formation appears to provide an increase in specificity and efficiency to the BER pathway, thereby facilitating the maintenance of genome integrity by preventing the accumulation of highly toxic repair intermediates [83]. Decreased concentrations of just one protein within this pathway could significantly alter the balance of complex formation, resulting in reduced repair capacity and an increased exposure to toxic BER intermediates, such as has been observed in pol ß deficiency in mouse cells [79,[91][92][93], in animal models [94] and in human cells [62].…”

“…Whether acetylated pol ß interacts with other BER proteins in the same manner as unacetylated pol ß remains to be seen. Nevertheless, p300 may have a novel regulatory role by modulating the critical pol ß 5'dRP lyase activity that is required for cellular survival following stress [93]. Given the dire consequences of abrogation of the pol ß 5'dRP lyase activity (cellular sensitivity to alkylating agents) [79,92,93], it seems likely that a de-acetylase, designed to reactivate pol ß 5'dRP lyase function, is present in vivo but to date has not been identified.…”

DNA polymerases in nonhomologous end joining: Are there any benefits to standing out from the crowd?

“…5 0 -dRP lyases cleave 3 0 of the 5 0 -dRP (or abasic site) through the formation of a Schiff base intermediate and b-elimination [Matsumoto and Kim, 1995;Piersen et al, 1996]. The 5 0 -dRP lyase activity in Pol b has an essential role in removing apurinic/apyrimidinic (AP) sites at strand break termini when flanked by extensive double-stranded DNA, as expected during base excision repair (BER) reactions [Sobol et al, 2000], but it is much less active near double-strand break termini [Roberts et al, 2010]. Even Pol4 activity, recruited to double-strand break ends by NHEJ core factors, is dispensable for 5 0 -dRP removal during joining in Saccharomyces cerevisiae [Daley and Wilson, 2008].…”

“…Pol b possesses DNA polymerase activity and dRP lyase activity, both of which are important to short patch BER [Sobol et al, 2000;Podlutsky et al, 2001]. Among the vertebrate Pol X members active on short gaps, its catalytic efficiency is comparable to Pol k [Brown et al, 2011], and much greater than Pol l [Roettger et al, 2004].…”

C1q/TNF‐related peptide 8 (CTRP8) promotes temozolomide resistance in human glioblastoma

“…The glycosylic backbone of the AP site is then cleaved by an AP lyase, like AP endonuclease 1 (APE1). This generates a cytotoxic 5′‐deoxyribosyl phosphate (dRP) residue which is commonly removed by the dRP lyase activity of DNA polymerase β (Sobol et al ., 2000). DNA polymerase β adds the complementary base and the X‐ray repair cross‐complementing group 1 (XRCC1)/DNA ligase III complex performs the phosphodiester bond formation to complete BER (Krokan and Bjoras, 2013).…”