FIG. 1.

Arrangement of conserved domains in yeast Pol3p (16) and locations of amino acid alterations in POL3 mutants. POL3 encodes a polypeptide of 124 kDa (1,097 amino acids). The coding sequence includes three regions corresponding to the exonuclease proofreading active site (Exo I, II, and III; Exo II is contained within domain IV). Other conserved domains include a catalytic center (domain I), regions thought to be involved in nucleotide binding (domains II, III, and V), and a putative zinc finger DNA binding domain (Zn) (58). A putative PCNA-interacting domain (PCNA) is located in the N-terminal region of the protein (61). The locations of the mutator alleles pol3-01 (37) and pol3-t (12) are shown in the upper half of the diagram. The amino acid substitutions of the unique POL3 missense and nonsense alleles characterized in this paper are indicated in the lower half of the diagram.