IDENTIFICATION OF 2 PROMOTERS WITHIN HUMAN CYTOMEGALOVIRUS MORPHOLOGIC TRANSFORMING REGION-II

A 980-bp subfragment of human cytomegalovirus (HCMV) strain Towne has been previously identified as morphologic transforming region II (mtrI I) because of its ability to induce focal transformation of NIH 3T3 ce lls. Transcripts from this region, which could encode the three open r eading frames (ORFs), 79, 83, and 34 amino acids (aa), detected by DNA sequence analysis, are expressed early during HC MV infection. In thi s report, the mRNA start sites for promoters (P1 and P2) were mapped w ithin Towne mtrII by primer extension using RNAs isolated from transfo rmed NIH 3T3 cells. The Towne mtrll promoters exhibited similar activi ties to the SV40 enhancerless early promoter. Equivalent promoter acti vities were detected within the mtrII colinear nontransforming region from HCMV strain Tanaka. Two subclones of Towne mtrII (5'440-bp and 3' 540-bp), each containing one promoter, were generated utilizing a uni que BgII site which also interrupted the 79-aa ORF. In transfection as says, neither the 5' 440-bp promoter subclone containing a truncated 7 9-aa ORF nor the 3' 540-bp subclone containing intact 83- and 34-aa OR Fs exhibited transforming activity. These data indicated that transfor mation by HCMV mtrll did not occur by promoter insertion. The identifi cation of these early promoters will allow further studies on the regu lation of important HCMV early genes known to be involved in viral/hos t interactions.