A MUTATIONAL ANALYSIS OF THE DNA-BINDING DOMAIN OF THE HERPES-SIMPLEXVIRUS TYPE-1 UL9-PROTEIN

The herpes simplex virus type 1 origin-binding protein is encoded by g ene UL9. We previously described a plasmid, pB1, which encodes a fusio n protein containing only the C-terminal 317 amino acids of the UL9 po lypeptide and showed that this product retains sequence-specific DNA-b inding ability. Two series of pB1 mutants have now been constructed an d the polypeptides were tested for origin-binding activity. Using C-te rminal truncations, we show that the C-terminal 34 amino acids of UL9 are dispensable for binding and that essential residues lie between po sitions 801 and 818. Analysis of a series of mutants containing insert ions of four amino acids at various positions identified regions of th e DNA-binding domain in which alterations either abolished or had rela tively little effect upon binding activity. Two mutants which were int ermediate in their binding activities also exhibited temperature- or s equence-specific effects.