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DNA polymerase mu (Pol μ), homologous to TdT, could act as a DNA mutator in eukaryotic cells
Author(s) -
Domínguez Orlando,
Ruiz José F.,
Laín de Lera Teresa,
GarcíaDíaz Miguel,
González Manuel A.,
Kirchhoff Tomas,
MartínezA Carlos,
Bernad Antonio,
Blanco Luis
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.7.1731
Subject(s) - dna polymerase , microbiology and biotechnology , dna polymerase i , dna polymerase mu , polymerase , dna polymerase ii , processivity , dna clamp , dna , biology , terminal deoxynucleotidyl transferase , dna polymerase delta , nucleotide , dna replication , gene , biochemistry , polymerase chain reaction , circular bacterial chromosome , reverse transcriptase , apoptosis , tunel assay
A novel DNA polymerase has been identified in human cells. Human DNA polymerase mu (Pol μ), consisting of 494 amino acids, has 41% identity to terminal deoxynucleotidyltransferase (TdT). Human Pol μ, overproduced in Escherichia coli in a soluble form and purified to homogeneity, displays intrinsic terminal deoxynucleotidyltransferase activity and a strong preference for activating Mn 2+ ions. Interestingly, unlike TdT, the catalytic efficiency of polymerization carried out by Pol μ was enhanced by the presence of a template strand. Using activating Mg 2+ ions, template‐enhanced polymerization was also template‐directed, leading to the preferred insertion of complementary nucleotides, although with low discrimination values. In the presence of Mn 2+ ions, template‐enhanced polymerization produced a random insertion of nucleotides. Northern‐blotting and in situ analysis showed a preferential expression of Pol μ mRNA in peripheral lymphoid tissues. Moreover, a large proportion of the human expressed sequence tags corresponding to Pol μ, present in the databases, derived from germinal center B cells. Therefore, Pol μ is a good candidate to be the mutator polymerase responsible for somatic hypermutation of immunoglobulin genes.