CONSERVATION IN HUMAN AND MOUSE PUR-ALPHA OF A MOTIF COMMON TO SEVERAL PROTEINS INVOLVED IN INITIATION OF DNA-REPLICATION

Pur alpha is a sequence-specific single-stranded DNA-binding protein w ith affinity for an element present in several eukaryotic origins of D NA replication (ori) and gene regulatory regions. We report here the c DNA sequence for mouse pur alpha and an extraordinary degree of conser vation between human and mouse Pur alpha (hPurA and mPurA, respectivel y). There are only two single-amino-acid (aa) changes between hPurA (3 22 aa) and mPurA (321 aa). One PurA region of 22 aa, termed the 'psych e' motif, possesses significant homology to a counterpart in the SV40 large T-antigen, to several other transforming proteins of DNA tumor v iruses, and to certain cellular proteins in yeast and human cells that may also be involved in the initiation of DNA replication.