Construction of a cloned library of the EcoRI fragments from the human cytomegalovirus genome (strain AD169)

Abstract

The MW of the DNA genome of human cytomegalovirus (HCMV) strain AD169 is 158 .times. 106. Cleavage of the HCMV DNA with the restriction endonuclease EcoRI yields 35 major fragments ranging in size from 0.54 .times. 106 to 11.4 .times. 106. A cloned library of the EcoRI fragments of this strain of HCMV was constructed using the plasmid pACYC184 and the recipient bacterium Escherichia coli strain HB101 RecA-. The viral origin of the cloned inserts was determined by hybridization to viral DNA. The fragments were characterized further by digestion with other restriction enzymes. Several clones were obtained which contained sequences spanning the junction between the long (L) and short (S) components of the viral DNA sequences. These clones differed in MW by multiples of 0.3 .times. 106-0.4 .times. 106. The variability found in the clones was also reflected in the genome. Each clone containing a junction sequence hybridized to a series of bands on Southern filters of EcoRI-digested HCMV DNA. This ladder effect provided evidence for a region of heterogeneity within the L-S junction.