REASSESSING THE ORGANIZATION OF THE UL42-UL43 REGION OF THE HUMAN CYTOMEGALOVIRUS STRAIN AD169 GENOME

A polymorphism in the UL42-UL43 region of the human cytomegalovirus ge nome has been characterized by nucleotide sequence analysis, revealing a 929-bp insertion following nt 54,612 relative to the published stra in AD169-UK genome sequence (M. S. Chee et al., 1990, Curr. Top. Micro biol. Immunol. 154, 125-170). Although AD169-UK exhibited polymorphism in this genomic region, other CMV strains (Towne, Toledo, and AD169-A TCC) carried only the newly characterized longer form. The additional sequence altered the assignment of UL42 and UL43 open reading frames. UL42 decreased in size from 157 to 125 codons, retaining 76 of the pre viously reported carboxyl terminal codons, and UL43 increased in size from 187 to 423 codons, retaining 185 of the previously reported amino terminal codons. this additional sequence makes UL43 a more conserved betaherpesvirus US22 family member. Only AD169-UK exhibited restricti on fragment length polymorphism in this region, suggesting that a dele tion occurred during the propagation of this strain in cell culture. T he additional sequence should be considered a bona fide part of the cy tomegalovirus genome and the AD169 genome size should be corrected to 230,283 bp. (C) 1997 Academic Press.