Abstract
We have defined the boundaries of the a sequence from human cytomegalovirus (CMV) strain Towne, characterized internal variability and determined the position of the cleavage site used to generate genomic termini. The cleavage site is positioned a fixed distance from two stretches of sequence homology that have been observed near the ends of many herpesvirus genomes. Unlike a comparable region in CMV (AD169), the CMV (Towne) a sequence has a relatively low level of variability within the a sequence and its structure is stable through repeated virus passage.