The downstream regulatory sequence of the adenovirus type 2 major late promoter is functionally redundant.

Mutagenesis of promoter sequences and oligonucleotide competition assays have been used to demonstrate the late-phase-specific stimulation of the adenovirus type 2 major late promoter is mediated by functionally redundant elements located between positions +75 and +125. These octamer motif-related sequences are recognized by multiple factors.     

Species dependence of the major late promoter in adenovirus type 12 DNA.

In hamster cells human adenovirus type 12 (Ad12) is deficient in DNA replication and late gene expression whereas adenovirus type 2 (Ad2) can replicate. Functions located in the E1 region of the Ad2 or adenovirus type 5 (Ad5) genome can complement the deficiencies of the Ad12 genome in hamster cells, but, infectious viral particles are not produced. We have now investigated the activity of the major late promoter of Ad2 and of Ad12 DNA in human and hamster cells. This promoter governs the expression of most of the late viral functions. We have inserted the major late promoter (MLP) of Ad2 or of Ad12 DNA in front of the chloramphenicol acetyl transferase gene in the pSVO-CAT construct. Upon transfection into uninfected human and hamster cells, the pAd12MLP-CAT construct shows no significant activity; the pAd2MLP-CAT construct exhibits low activity. In Ad12-infected human cells, both constructs are active. These findings support the notion that other viral factors are required for MLP activity of Ad2 or Ad12 DNA in permissive human cells. In Ad2-infected hamster cells, both the pAd2MLP-CAT and the pAd12MLP-CAT constructs are active. Apparently, the Ad12 MLP can be activated by Ad2 functions, as already demonstrated for the entire Ad12 genome in double-infected cells or in Ad2- or Ad5-transformed cells superinfected with Ad12. In Ad12-infected hamster cells, however, the MLP of Ad12 DNA is inactive but that of Ad2 DNA shows activity. Thus the MLP of Ad12 DNA somehow differentiates between cellular auxiliary functions of different species.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phosphorylation-dependent binding of a 138-kDa myc intron factor to a regulatory element in the first intron of the c-myc gene

A 138-kDa nuclear protein was identified from HeLa cell extracts as a factor which binds to a previously described 20-base pair cis element located in the intron I of the c-myc gene. This myc intron factor (MIF) binds to the wild type c-myc sequence but does not bind under similar conditions to c-myc from Burkitt's lymphoma which contain point mutations in this binding region. We have demonstrated that the 138-kDa MIF is a phosphoprotein and that treatment of the purified MIF with potato acid phosphatase abolished binding to its 20-base pair c-myc recognition sequence; binding activity was protected by inclusion of phosphatase inhibitors. These results suggest that phosphorylation is required for the specific DNA-MIF interaction in vitro and that the phosphorylation state of MIF may be an important factor in controlling c-myc expression in vivo.