* 174760

POLYMERASE, DNA, BETA; POLB


HGNC Approved Gene Symbol: POLB

Cytogenetic location: 8p11.21     Genomic coordinates (GRCh38): 8:42,338,494-42,371,808 (from NCBI)


TEXT

Description

In eukaryotic cells, DNA polymerase beta (POLB) carries out base-excision repair (BER) that is required for DNA maintenance, replication, recombination, and drug resistance (summary by Bhattacharyya and Banerjee, 1997). Also see POLA (312040).


Gene Function

Two important enzymatic steps in mammalian BER are contributed by POLB: DNA resynthesis of the repair patch and lyase removal of the 5-prime-deoxyribose phosphate. Fibroblasts from PolB-null mice are hypersensitive to monofunctional DNA-methylating agents, resulting in increases in chromosomal damage, apoptosis, and necrotic cell death. Sobol et al. (2000) demonstrated that only the 5-prime-deoxyribose phosphate lyase activity of PolB is required to reverse methylating agent hypersensitivity in PolB-null cells. Sobol et al. (2000) concluded that their results indicate that removal of the deoxyribose phosphate group is a pivotal step in BER in vivo. Persistence of the deoxyribose phosphate moiety in DNA results in the hypersensitivity phenotype of PolB-null cells and may signal downstream events such as apoptosis and necrotic cell death.

Since DNA polymerase beta functions in both base excision repair and meiosis, errors committed by polymerase beta during these processes could result in mutations. Using a complementation system in which rat DNA polymerase beta substituted for DNA polymerase I of Escherichia coli, Clairmont and Sweasy (1996) isolated a DNA polymerase beta mutant in which tyr265 was changed to cys (Y265C). The Y265C mutant was dominant to wildtype DNA polymerase beta and possessed an intrinsic mutator activity. Clairmont et al. (1999) expressed the wildtype DNA polymerase and the Y265C mutator mutant in mouse LN12 cells, which have endogenous DNA polymerase beta activity. They demonstrated that expression of the Y265C mutator mutant in the LN12 cells resulted in an 8-fold increase in the spontaneous mutation frequency of lambda-cII mutants compared to expression of the wildtype protein. Expression of Y265C resulted in at least a 40-fold increase in the frequency of deletions of 3 bases or more and a 7-fold increase in point mutations. The results suggested that the mutations observed in vivo resulted directly from the action of the mutator polymerase. This appeared to be the first demonstration of a mutator phenotype resulting from expression of a DNA polymerase mutator mutant in mammalian cells. The work raised the possibility that variant polymerases may act in a dominant fashion in human cells, leading to genetic instability and carcinogenesis.

Bhattacharyya and Banerjee (1997) found that a truncated POLB is expressed in primary colorectal tumors and inhibits the normal repair function of wildtype POLB. Bhattacharyya and Banerjee (2001) determined that the truncated polymerase interacts with XRCC1 (194360) and that this binding is required for the dominant-negative effect.

Because POLB and the clinical phenotype of Werner syndrome (WRN; 277700) map to the same region, 8p12-p11, Sadakane et al. (1994) investigated the POLB gene in 2 patients and found 107-bp insertions or 87-bp deletions in the catalytic domain. Further study was required to determine whether this is a primary or a secondary change, since somatic cells from Werner syndrome patients have a propensity to develop chromosomal aberrations. Chang et al. (1994) used fluorescence in situ hybridization to place the POLB gene centromeric to D8S135 at 8p11.2. This and other evidence presented by Chang et al. (1994) indicated that POLB is not the Werner syndrome gene.

El-Andaloussi et al. (2006) determined that human POLB formed a complex with and was methylated by PRMT6 (608274). In vitro, methylated POLB possessed significantly higher DNA polymerase activity when compared to that of unmodified enzyme. The increase in DNA polymerase activity upon methylation was due to the enhanced DNA binding and processivity of POLB.


Gene Structure

Chyan et al. (1994) found that the POLB gene spans 33 kb and contains 14 exons that range in size from 50 to 233 bp. The 13 introns vary from 96 bp to 6.5 kb. They defined the location of a deletion/insertion type of RFLP 5-prime to exon 1 of the POLB gene and used this RFLP in linkage analysis of DNAs from CEPH families to confirm the assignment of the gene to 8p12-p11. Analysis of mRNA from 6 human cell lines demonstrated alternative splicing, with one type of transcript lacking the 58 bp of exon 2.


Mapping

Using a cDNA for beta polymerase of the rat, McBride et al. (1987) mapped the human gene for beta polymerase to chromosome 8 by Southern analysis of DNAs isolated from human-rodent somatic cell hybrids. During this study, they also detected a human DNA restriction fragment length polymorphism in normal individuals by using a probe from the 5-prime end of the beta polymerase cDNA. They proposed that this RFLP might be used in determining the possible role of a defect in the POLB gene in various human hereditary disorders. The POLB gene was found to be in single copy and to be located on the short arm or proximal long arm of chromosome 8 (8pter-q22). Cannizzaro et al. (1988) used a cDNA clone for POLB to map the gene to 8p12-p11 by a combination of somatic cell and in situ hybridization. McBride et al. (1990) localized the mouse counterpart (Polb) to chromosome 8 by Southern analysis of mouse/hamster somatic cell hybrids as well as by linkage analysis in an interspecific backcross.


REFERENCES

  1. Bhattacharyya, N., Banerjee, S. A variant of DNA polymerase beta acts as a dominant negative mutant. Proc. Nat. Acad. Sci. 94: 10324-10329, 1997. [PubMed: 9294209, images, related citations] [Full Text]

  2. Bhattacharyya, N., Banerjee, S. A novel role of XRCC1 in the functions of a DNA polymerase beta variant. Biochemistry 40: 9005-9013, 2001. [PubMed: 11467963, related citations] [Full Text]

  3. Cannizzaro, L. A., Bollum, F. J., Huebner, K., Croce, C. M., Cheung, L. C., Xu, X., Hecht, B. K., Hecht, F., Chang, L. M. S. Chromosome sublocalization of a cDNA for human DNA polymerase-beta to 8p11-p12. Cytogenet. Cell Genet. 47: 121-124, 1988. [PubMed: 3378450, related citations] [Full Text]

  4. Chang, M., Burmer, G. C., Sweasy, J., Loeb, L. A., Edelhoff, S., Disteche, C. M., Yu, C.-E., Anderson, L., Oshima, J., Nakura, J., Miki, T., Kamino, K., Ogihara, T., Schellenberg, G. D., Martin, G. M. Evidence against DNA polymerase beta as a candidate gene for Werner syndrome. Hum. Genet. 93: 507-512, 1994. [PubMed: 8168825, related citations] [Full Text]

  5. Chyan, Y.-J., Ackerman, S., Shepherd, N. S., McBride, O. W., Widen, S. G., Wilson, S. H., Wood, T. G. The human DNA polymerase beta gene structure: evidence of alternative splicing in gene expression. Nucleic Acids Res. 22: 2719-2725, 1994. [PubMed: 7914364, related citations] [Full Text]

  6. Clairmont, C. A., Narayanan, L., Sun, K.-W., Glazer, P. M., Sweasy, J. B. The tyr-265-to-cys mutator mutant of DNA polymerase beta induces a mutator phenotype in mouse LN12 cells. Proc. Nat. Acad. Sci. 96: 9580-9585, 1999. [PubMed: 10449735, images, related citations] [Full Text]

  7. Clairmont, C. A., Sweasy, J. B. Dominant negative rat DNA polymerase beta mutants interfere with base excision repair in Saccharomyces cerevisiae. J. Bact. 178: 656-661, 1996. [PubMed: 8550496, related citations] [Full Text]

  8. El-Andaloussi, N., Valovka, T., Toueille, M., Steinacher, R., Focke, F., Gehrig, P., Covic, M., Hassa, P. O., Schar, P., Hubscher, U., Hottiger, M. O. Arginine methylation regulates DNA polymerase beta. Molec. Cell 22: 51-62, 2006. [PubMed: 16600869, related citations] [Full Text]

  9. McBride, O. W., Kozak, C. A., Wilson, S. H. Mapping of the gene for DNA polymerase beta to mouse chromosome 8. Cytogenet. Cell Genet. 53: 108-111, 1990. [PubMed: 1973375, related citations] [Full Text]

  10. McBride, O. W., Zmudzka, B. Z., Wilson, S. H. Chromosomal location of the human gene for DNA polymerase beta. Proc. Nat. Acad. Sci. 84: 503-507, 1987. [PubMed: 3467369, related citations] [Full Text]

  11. Sadakane, Y., Maeda, K., Kuroda, Y., Hori, K. Identification of mutations in DNA polymerase beta mRNAs from patients with Werner syndrome. Biochem. Biophys. Res. Commun. 200: 219-225, 1994. [PubMed: 7545922, related citations] [Full Text]

  12. Sobol, R. W., Prasad, R., Evenski, A., Baker, A., Yang, X.-P., Horton, J. K., Wilson, S. H. The lyase activity of the DNA repair protein beta-polymerase protects from DNA-damage-induced cytotoxicity. Nature 405: 807-810, 2000. [PubMed: 10866204, related citations] [Full Text]


Patricia A. Hartz - updated : 5/3/2006
Patricia A. Hartz - updated : 4/4/2002
Ada Hamosh - updated : 7/17/2000
Victor A. McKusick - updated : 9/24/1999
Creation Date:
Victor A. McKusick : 6/2/1986
carol : 07/26/2011
wwang : 5/12/2006
terry : 5/3/2006
carol : 4/4/2002
alopez : 7/20/2000
terry : 7/17/2000
alopez : 10/20/1999
terry : 9/24/1999
carol : 2/3/1995
jason : 6/13/1994
supermim : 3/16/1992
supermim : 9/28/1990
supermim : 3/20/1990
ddp : 10/27/1989

* 174760

POLYMERASE, DNA, BETA; POLB


HGNC Approved Gene Symbol: POLB

Cytogenetic location: 8p11.21     Genomic coordinates (GRCh38): 8:42,338,494-42,371,808 (from NCBI)


TEXT

Description

In eukaryotic cells, DNA polymerase beta (POLB) carries out base-excision repair (BER) that is required for DNA maintenance, replication, recombination, and drug resistance (summary by Bhattacharyya and Banerjee, 1997). Also see POLA (312040).


Gene Function

Two important enzymatic steps in mammalian BER are contributed by POLB: DNA resynthesis of the repair patch and lyase removal of the 5-prime-deoxyribose phosphate. Fibroblasts from PolB-null mice are hypersensitive to monofunctional DNA-methylating agents, resulting in increases in chromosomal damage, apoptosis, and necrotic cell death. Sobol et al. (2000) demonstrated that only the 5-prime-deoxyribose phosphate lyase activity of PolB is required to reverse methylating agent hypersensitivity in PolB-null cells. Sobol et al. (2000) concluded that their results indicate that removal of the deoxyribose phosphate group is a pivotal step in BER in vivo. Persistence of the deoxyribose phosphate moiety in DNA results in the hypersensitivity phenotype of PolB-null cells and may signal downstream events such as apoptosis and necrotic cell death.

Since DNA polymerase beta functions in both base excision repair and meiosis, errors committed by polymerase beta during these processes could result in mutations. Using a complementation system in which rat DNA polymerase beta substituted for DNA polymerase I of Escherichia coli, Clairmont and Sweasy (1996) isolated a DNA polymerase beta mutant in which tyr265 was changed to cys (Y265C). The Y265C mutant was dominant to wildtype DNA polymerase beta and possessed an intrinsic mutator activity. Clairmont et al. (1999) expressed the wildtype DNA polymerase and the Y265C mutator mutant in mouse LN12 cells, which have endogenous DNA polymerase beta activity. They demonstrated that expression of the Y265C mutator mutant in the LN12 cells resulted in an 8-fold increase in the spontaneous mutation frequency of lambda-cII mutants compared to expression of the wildtype protein. Expression of Y265C resulted in at least a 40-fold increase in the frequency of deletions of 3 bases or more and a 7-fold increase in point mutations. The results suggested that the mutations observed in vivo resulted directly from the action of the mutator polymerase. This appeared to be the first demonstration of a mutator phenotype resulting from expression of a DNA polymerase mutator mutant in mammalian cells. The work raised the possibility that variant polymerases may act in a dominant fashion in human cells, leading to genetic instability and carcinogenesis.

Bhattacharyya and Banerjee (1997) found that a truncated POLB is expressed in primary colorectal tumors and inhibits the normal repair function of wildtype POLB. Bhattacharyya and Banerjee (2001) determined that the truncated polymerase interacts with XRCC1 (194360) and that this binding is required for the dominant-negative effect.

Because POLB and the clinical phenotype of Werner syndrome (WRN; 277700) map to the same region, 8p12-p11, Sadakane et al. (1994) investigated the POLB gene in 2 patients and found 107-bp insertions or 87-bp deletions in the catalytic domain. Further study was required to determine whether this is a primary or a secondary change, since somatic cells from Werner syndrome patients have a propensity to develop chromosomal aberrations. Chang et al. (1994) used fluorescence in situ hybridization to place the POLB gene centromeric to D8S135 at 8p11.2. This and other evidence presented by Chang et al. (1994) indicated that POLB is not the Werner syndrome gene.

El-Andaloussi et al. (2006) determined that human POLB formed a complex with and was methylated by PRMT6 (608274). In vitro, methylated POLB possessed significantly higher DNA polymerase activity when compared to that of unmodified enzyme. The increase in DNA polymerase activity upon methylation was due to the enhanced DNA binding and processivity of POLB.


Gene Structure

Chyan et al. (1994) found that the POLB gene spans 33 kb and contains 14 exons that range in size from 50 to 233 bp. The 13 introns vary from 96 bp to 6.5 kb. They defined the location of a deletion/insertion type of RFLP 5-prime to exon 1 of the POLB gene and used this RFLP in linkage analysis of DNAs from CEPH families to confirm the assignment of the gene to 8p12-p11. Analysis of mRNA from 6 human cell lines demonstrated alternative splicing, with one type of transcript lacking the 58 bp of exon 2.


Mapping

Using a cDNA for beta polymerase of the rat, McBride et al. (1987) mapped the human gene for beta polymerase to chromosome 8 by Southern analysis of DNAs isolated from human-rodent somatic cell hybrids. During this study, they also detected a human DNA restriction fragment length polymorphism in normal individuals by using a probe from the 5-prime end of the beta polymerase cDNA. They proposed that this RFLP might be used in determining the possible role of a defect in the POLB gene in various human hereditary disorders. The POLB gene was found to be in single copy and to be located on the short arm or proximal long arm of chromosome 8 (8pter-q22). Cannizzaro et al. (1988) used a cDNA clone for POLB to map the gene to 8p12-p11 by a combination of somatic cell and in situ hybridization. McBride et al. (1990) localized the mouse counterpart (Polb) to chromosome 8 by Southern analysis of mouse/hamster somatic cell hybrids as well as by linkage analysis in an interspecific backcross.


REFERENCES

  1. Bhattacharyya, N., Banerjee, S. A variant of DNA polymerase beta acts as a dominant negative mutant. Proc. Nat. Acad. Sci. 94: 10324-10329, 1997. [PubMed: 9294209] [Full Text: https://doi.org/10.1073/pnas.94.19.10324]

  2. Bhattacharyya, N., Banerjee, S. A novel role of XRCC1 in the functions of a DNA polymerase beta variant. Biochemistry 40: 9005-9013, 2001. [PubMed: 11467963] [Full Text: https://doi.org/10.1021/bi0028789]

  3. Cannizzaro, L. A., Bollum, F. J., Huebner, K., Croce, C. M., Cheung, L. C., Xu, X., Hecht, B. K., Hecht, F., Chang, L. M. S. Chromosome sublocalization of a cDNA for human DNA polymerase-beta to 8p11-p12. Cytogenet. Cell Genet. 47: 121-124, 1988. [PubMed: 3378450] [Full Text: https://doi.org/10.1159/000132527]

  4. Chang, M., Burmer, G. C., Sweasy, J., Loeb, L. A., Edelhoff, S., Disteche, C. M., Yu, C.-E., Anderson, L., Oshima, J., Nakura, J., Miki, T., Kamino, K., Ogihara, T., Schellenberg, G. D., Martin, G. M. Evidence against DNA polymerase beta as a candidate gene for Werner syndrome. Hum. Genet. 93: 507-512, 1994. [PubMed: 8168825] [Full Text: https://doi.org/10.1007/BF00202813]

  5. Chyan, Y.-J., Ackerman, S., Shepherd, N. S., McBride, O. W., Widen, S. G., Wilson, S. H., Wood, T. G. The human DNA polymerase beta gene structure: evidence of alternative splicing in gene expression. Nucleic Acids Res. 22: 2719-2725, 1994. [PubMed: 7914364] [Full Text: https://doi.org/10.1093/nar/22.14.2719]

  6. Clairmont, C. A., Narayanan, L., Sun, K.-W., Glazer, P. M., Sweasy, J. B. The tyr-265-to-cys mutator mutant of DNA polymerase beta induces a mutator phenotype in mouse LN12 cells. Proc. Nat. Acad. Sci. 96: 9580-9585, 1999. [PubMed: 10449735] [Full Text: https://doi.org/10.1073/pnas.96.17.9580]

  7. Clairmont, C. A., Sweasy, J. B. Dominant negative rat DNA polymerase beta mutants interfere with base excision repair in Saccharomyces cerevisiae. J. Bact. 178: 656-661, 1996. [PubMed: 8550496] [Full Text: https://doi.org/10.1128/jb.178.3.656-661.1996]

  8. El-Andaloussi, N., Valovka, T., Toueille, M., Steinacher, R., Focke, F., Gehrig, P., Covic, M., Hassa, P. O., Schar, P., Hubscher, U., Hottiger, M. O. Arginine methylation regulates DNA polymerase beta. Molec. Cell 22: 51-62, 2006. [PubMed: 16600869] [Full Text: https://doi.org/10.1016/j.molcel.2006.02.013]

  9. McBride, O. W., Kozak, C. A., Wilson, S. H. Mapping of the gene for DNA polymerase beta to mouse chromosome 8. Cytogenet. Cell Genet. 53: 108-111, 1990. [PubMed: 1973375] [Full Text: https://doi.org/10.1159/000132906]

  10. McBride, O. W., Zmudzka, B. Z., Wilson, S. H. Chromosomal location of the human gene for DNA polymerase beta. Proc. Nat. Acad. Sci. 84: 503-507, 1987. [PubMed: 3467369] [Full Text: https://doi.org/10.1073/pnas.84.2.503]

  11. Sadakane, Y., Maeda, K., Kuroda, Y., Hori, K. Identification of mutations in DNA polymerase beta mRNAs from patients with Werner syndrome. Biochem. Biophys. Res. Commun. 200: 219-225, 1994. [PubMed: 7545922] [Full Text: https://doi.org/10.1006/bbrc.1994.1437]

  12. Sobol, R. W., Prasad, R., Evenski, A., Baker, A., Yang, X.-P., Horton, J. K., Wilson, S. H. The lyase activity of the DNA repair protein beta-polymerase protects from DNA-damage-induced cytotoxicity. Nature 405: 807-810, 2000. [PubMed: 10866204] [Full Text: https://doi.org/10.1038/35015598]


Contributors:
Patricia A. Hartz - updated : 5/3/2006
Patricia A. Hartz - updated : 4/4/2002
Ada Hamosh - updated : 7/17/2000
Victor A. McKusick - updated : 9/24/1999

Creation Date:
Victor A. McKusick : 6/2/1986

Edit History:
carol : 07/26/2011
wwang : 5/12/2006
terry : 5/3/2006
carol : 4/4/2002
alopez : 7/20/2000
terry : 7/17/2000
alopez : 10/20/1999
terry : 9/24/1999
carol : 2/3/1995
jason : 6/13/1994
supermim : 3/16/1992
supermim : 9/28/1990
supermim : 3/20/1990
ddp : 10/27/1989