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 with affinity for an element present in several eukaryotic origins of DNA replication (ori) and gene regulatory regions. We report here the cDNA sequence for mouse pur alpha and an extraordinary degree of conservation between human and mouse Pur alpha (hPurA and mPurA, respectively). There are only two single-amino-acid (aa) changes between hPurA (322 aa) and mPurA (321 aa). One PurA region of 22 aa, termed the 'psycho' motif, possesses significant homology to a counterpart in the SV40 large T-antigen, to several other transforming proteins of DNA tumor viruses, and to certain cellular proteins in yeast and human cells that may also be involved in the initiation of DNA replication.