Primary structure of the catalytic subunits of bovine and human DNA polymerase delta

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Biochemistry and Molecular Biology

First Committee Member

Antero G. So, Committee Chair


DNA polymerase $\delta$ (pol $\delta$) is one of at least two DNA polymerases required to replicate chromosomal DNA in eukaryotic cells. Pol $\delta$ from all eukaryotes is a heterodimer with subunits of about 125- and 50-kDa. The 125-kDa subunit contains both polymerase and $3\sp\prime$-$5\sp\prime$ exonuclease activities while the function of the 50-kDa subunit remains unknown.To elucidate the primary structure of the catalytic subunit of pol $\delta$, the nucleotide sequences of full-length cDNAs encoding the catalytic subunits of both bovine and human pol $\delta$s have been determined by polymerase chain reaction methodology (PCR). The gene encoding the catalytic subunit of human pol $\delta$ has been localized to chromosome 19 by PCR analysis of DNA from a panel of human-hamster hybrid cells. In addition, the catalytic subunit of human pol $\delta$ has been expressed in Escherichia coli.The nucleotide sequences of the cDNAs for the catalytic subunits of human and bovine pol $\delta$ predict polypeptides of 1107 amino acids for the human enzyme and 1106 amino acids for the bovine one, with a calculated molecular weight of 124,000 daltons for both. The human polypeptide is 94% identical to the bovine enzyme. The catalytic subunits of both bovine and human pol $\delta$s contain the seven conserved regions found in a number of bacterial, phage, viral and eukaryotic DNA polymerases. They also contain five additional regions that are highly conserved among $\delta$ polymerases but share little or no similarity with the $\alpha$ polymerases. Four of these regions are also similar to corresponding regions in the herpes virus family of DNA polymerases, whereas one region is apparently unique to the $\delta$ polymerases. In addition, the $\delta$ enzymes contain two putative zinc finger domains which may be involved in DNA binding in the carboxyl terminal region of the protein as well as potential nuclear localization signal (NLS) sequence motifs found in other nuclear proteins.


Biology, Molecular

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