CONSERVATION OF DNA-SEQUENCE IN THE PREDICTED MAJOR LATE PROMOTER REGIONS OF SELECTED MASTADENOVIRUSES

The major late promoter (MLP) of the subgroup C human adenoviruses is a preeminent model for the study of the mechanisms of basal and activa ted transcription, both in vivo and in vitro. However, while the struc ture and function of the human virus MLP has been the subject of exten sive investigation, the conservation of the various promoter elements among the adenoviruses from different species has not been examined. C onservation of specific elements would strongly suggest the importance and universality of their function. To address this issue, sequences were obtained from cloned DNAs of several representative Mastadenoviri dae, mouse adenovirus type 1 (MAV-1), Tupaia adenovirus type 1 (TAV-1) , and two bovine adenoviruses of two distinct subgroups, BAV-3 and BAV -7. The results of the sequencing studies showed that the TATA box and an upstream inverted CAAT box are conserved in all species and that t he binding site for transcription factor USF is present in all except MAV-1, in which a sequence similar to an Spl-binding site is present a t a similar position. The initiator element (INR) sequence is nor well conserved, and only one or other of the two downstream activating ele ments, DE1 and DE2, is predicted to be present in the nonprimate virus MLP regions. Ribonuclease protection assays on RNA isolated from MAV- 1-infected cells late in infection indicated that the predicted MLP is functional, and transcription initiation and splice donor sites were identified. The human virus MLP is embedded in the essential DNA polym erase sequence on the opposite DNA strand. The primary amino acid sequ ences of the C-terminal regions of the predicted DNA polymerases show strong conservation of sequence motifs observed in replicative polymer ases ranging from prokaryotes to mammals, and additional regions of st rong conservation among the adenovirus polymerases. Pairwise compariso ns between the newly sequenced regions of the polymerases and previous ly published sequences show that BAV-7 is most dissimilar to all other s, while TAV-1 has a greater similarity to the primate sequences than to the others. The sequence data from both strands were also used to c onstruct phylogenetic trees, based on BAV-7 as the outgroup. The trees constructed from the two sets of sequences are broadly similar, showi ng close relationships between primate viruses, but differing in the o rder of divergence of TAV-1 and MAV-1 branches. (C) 1996 Academic Pres s, Inc.