Disease relevance of POLB

• Recurrent homogeneously staining regions in 8p1 in breast cancer and lack of amplification of POLB, LHRH, and PLAT genes [1].
• Expression of human DNA polymerase beta in Escherichia coli and characterization of the recombinant enzyme [2].
• DNA polymerase beta mutations in human colorectal cancer [3].
• The single base insertion was also observed in our previous study of human prostate cancer, suggesting that this region may be a hot spot for mutation of the DNA polymerase beta gene [4].
• Elevated DNA polymerase alpha, DNA polymerase beta, and DNA topoisomerase II in a melphalan-resistant rhabdomyosarcoma xenograft that is cross-resistant to nitrosoureas and topotecan [5].

High impact information on POLB

• Here, we report that XRCC1 interacts with human polynucleotide kinase in addition to its established interactions with DNA polymerase-beta and DNA ligase III [6].
• Arginine methylation regulates DNA polymerase beta [7].
• NEIL1 stably interacts with other BER proteins, DNA polymerase beta (pol beta) and DNA ligase IIIalpha [8].
• We describe a novel regulatory mechanism for DNA polymerase beta (Polbeta), a protein involved in DNA base excision repair (BER) [9].
• Acetylation regulates the DNA end-trimming activity of DNA polymerase beta [9].

Chemical compound and disease context of POLB

• Elevated expression of DNA polymerase beta gene in glioma cell lines with acquired resistance to 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3- nitrosourea [10].
• We investigated the expression of DNA polymerase beta (beta-pol) and O6-methylguanine-DNA methyltransferase (MGMT) in human glioma cells with acquired resistance to 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoure a (ACNU) and in the parent cells [10].
• Hypothermic treatment diminished the serine-specific phosphorylation of AP endonuclease and DNA polymerase-beta, promoted BER activities, and attenuated the levels of oxidative DNA lesions after ischemia [11].
• A protein fraction isolated from the cytosol of adenovirus-infected HeLa cells, which contained DNA polymerase alpha, catalyzed adenoviral DNA replication in the presence of adenovirus DNA binding protein, eukaryotic DNA polymerase beta, ATP, all four dNTPs, and MgCl2 [12].
• For instance, as little as 1 microM BVdUTP inhibited the utilization of dTTP by HSV-1 DNA polymerase 50%, whereas the same concentration inhibited the DNA polymerase alpha and the DNA polymerase beta activities only 9% and 3%, respectively [13].

Biological context of POLB

• Single strand conformation polymorphism (SSCP) analysis and direct sequencing of POLB cDNA derived from cell lines and tumors, many with known deletions of proximal 8p, revealed one sequence variant that was shown to represent a normal sequence polymorphism [14].
• It is not certain at this point, whether POLB and HPRT splice variants are the result of regulated alternative splicing processes or the result of aberrant splicing, but it appears likely that at least some of the variants are the result of splicing errors [15].
• Reconstitution of DNA base excision-repair with purified human proteins: interaction between DNA polymerase beta and the XRCC1 protein [16].
• Mutations in the catalytic domain of DNA polymerase beta were detected in colorectal tumor specimens compared to the normal colorectal mucosa, placenta, and blood samples [3].
• A novel nuclear protein, MGC5306 interacts with DNA polymerase beta and has a potential role in cellular phenotype [17].

Anatomical context of POLB

• In eukaryotic cells, DNA polymerase beta (polbeta) carries out base-excision repair (BER) required for DNA maintenance, replication, recombination, and drug resistance [18].
• The capacity of stimulated lymphocytes to perform repair synthesis following UV damage was measured in the same cells used for the enzyme activity determinations; this capacity also shows two maxima: a first one correlated with the peak in DNA replication rate, and a second one correlated with the peak of DNA polymerase-beta [19].
• Two enzymes of base excision repair (BER), uracil DNA glycosylase (UDG) and DNA polymerase beta (beta pol), from HeLa cells co-eluted from Superose 12 FPLC columns [20].
• DNA polymerase beta and GSH levels were, however, higher than those in a line of normal skin fibroblasts [21].
• DNA polymerase beta can also stimulate the synthesis of adenovirus DNA in vitro in the presence of a cytosol extract from adenovirus-infected cells [22].

Associations of POLB with chemical compounds

• We found that UDG and APE carry out their catalytic activities with reduced efficiency on nucleosome substrates, showing a distinction between uracil facing 'out' or 'in' from the histone surface, while DNA polymerase beta (pol beta) is completely inhibited by nucleosome formation [23].
• Upon binding a correct deoxynucleoside triphosphate, alpha-helix N of DNA polymerase beta is observed to form one face of the binding pocket for the new base pair [24].
• We have found that an 8-oxoguanine located opposite to an abasic site does not affect either the efficiency or fidelity of repair synthesis by DNA polymerase beta [25].
• Excision of C-4'-oxidized deoxyribose lesions from double-stranded DNA by human apurinic/apyrimidinic endonuclease (Ape1 protein) and DNA polymerase beta [26].
• Covalent trapping of human DNA polymerase beta by the oxidative DNA lesion 2-deoxyribonolactone [27].

Physical interactions of POLB

• We show that XRCC1 interacts directly with DNA polymerase beta using far Western blotting, affinity precipitation and yeast two-hybrid analyses [16].
• In addition, DNA ligase I participates in a second BER pathway that is carried out by a multiprotein complex in which DNA ligase I interacts directly with DNA polymerase beta [28].
• WRN interacts with DNA polymerase beta (pol beta) and stimulates pol beta strand displacement synthesis on a base excision repair (BER) intermediate in a helicase-dependent manner [29].
• The human Rad9/Rad1/Hus1 damage sensor clamp interacts with DNA polymerase beta and increases its DNA substrate utilisation efficiency: implications for DNA repair [30].

Enzymatic interactions of POLB

• The recent observation that Ape1-cleaved dL sites can covalently trap DNA polymerase beta during the abasic excision process suggests that efficient incision of dL by Ape1 may potentiate further problems in DNA repair [31].
• The 3'-5' exonuclease activity is considered important in proofreading of DNA synthesis catalyzed by DNA polymerase beta [32].
• With DNA primers, DNA polymerase alpha catalyzes only limited deoxynucleotide addition whereas DNA polymerase beta alone elongates DNA primed templates to full length [22].

Co-localisations of POLB

• The kinetoplast structure-specific endonuclease I is related to the 5' exo/endonuclease domain of bacterial DNA polymerase I and colocalizes with the kinetoplast topoisomerase II and DNA polymerase beta during replication [33].

Regulatory relationships of POLB

• We have previously reported that WRN helicase activity stimulates DNA polymerase beta (pol beta) strand displacement synthesis in vitro [34].
• PARP-1 stimulates strand displacement DNA synthesis by DNA polymerase beta in this system; this stimulation is dependent on the presence of FEN-1 [35].
• We find that binding of the 8-oxoguanine-DNA glycosylase to this 8-oxoguanine residue inhibits DNA repair synthesis by DNA polymerase beta, thus delaying repair [36].
• Thus, emergence of a higher level of resistance to MMC in J82/MMC-2 cells compared with J82/MMC may be attributed to (i) impaired drug activation through further reduction in DT-diaphorase activity and (ii) enhanced DNA repair through over-expression of DNA polymerase beta [37].
• Telomere repeat binding factor 2 interacts with base excision repair proteins and stimulates DNA synthesis by DNA polymerase beta [38].

Other interactions of POLB

• In higher eukaryotes, base excision repair can proceed by two alternative pathways: a DNA polymerase beta-dependent pathway and a proliferating cell nuclear antigen (PCNA)-dependent pathway [39].
• Differential regulation by p21 is likely to relate to the utilization of DNA polymerase beta, which is not sensitive to p21, in the repair pathway [40].
• Mutation analysis of 8p genes POLB and PPP2CB in bladder cancer [14].
• Human AP endonuclease, DNA polymerase beta and a DNA ligase (either III or I) were sufficient for the repair of a regular AP site [41].
• The XRCC1 protein, which is known to bind DNA ligase III, is not absolutely required for the reaction but suppresses strand displacement by DNA polymerase beta, allowing for more efficient ligation after filling of a single nucleotide patch [16].

Analytical, diagnostic and therapeutic context of POLB

• In addition, a complex formed between DNA polymerase beta and a double-stranded oligonucleotide containing an incised abasic site was supershifted by XRCC1 in a gel retardation assay [16].
• We examined 24 human bladder cancer tissues for possible mutations in the entire coding region of the human DNA polymerase beta gene using polymerase chain reaction analysis, single-strand conformational polymorphism analysis of RNA, and sequence analysis [4].
• DNA polymerase beta transcripts were analyzed in 8 breast cancer cell lines, snap-frozen benign breast tissues from 10 women, and lymphocytes from 10 normal controls, using reverse-transcription polymerase chain reaction (RT-PCR) and three separate primer pairs [42].
• Further, the truncated POLB could be demonstrated in both cancer focus and cancer adjacent tissues, but could not be found in the corresponding normal tissue in immunoblotting [43].
• We determined the error spectrum of DNA polymerase beta in the human APC gene under PCR conditions and compared it with the set of mutations reported in human colon tumors [44].

References