The human transforming growth factor alpha promoter directs transcription initiation from a single site in the absence of a TATA sequence.

Transforming growth factor alpha (TGF-alpha) is a transformation-responsive mitogenic polypeptide that is expressed in the brain, epithelial cells, and activated macrophages. We isolated and characterized the TGF-alpha promoter and localized the 5' end of the TGF-alpha transcript to a unique position. Surprisingly, no apparent TATA box was present in the promoter sequence, suggesting that transcription from mammalian genes can initiate at unique and specific positions from promoters lacking this sequence motif.

A discrete element 3' of human immunodeficiency virus 1 (HIV-1) and HIV-2 mRNA initiation sites mediates transcriptional activation by an HIV trans activator.

An important point of regulation in the reproductive growth and latency of the human and simian immunodeficiency viruses (HIV and SIV, respectively) is provided by virally encoded trans-activators (tat), proteins capable of dramatically increasing viral gene expression. The mechanism of this autostimulatory pathway has remained unclear, however, with substantial effects having been reported at the level of either mRNA accumulation, translational efficiency, or both. Our previous findings indicated that trans-activation results primarily from induction of RNA levels but could not distinguish between the roles of transcriptional rate, RNA stabilization, and RNA transport in this event.

Definition of regions in human c-myc that are involved in transformation and nuclear localization.

To study the relationship between the primary structure of the c-myc protein and some of its functional properties, we made in-frame insertion and deletion mutants of the normal human c-myc coding domain that was expressed from a retroviral promoter-enhancer. We assessed the effects of these mutations on the ability of c-myc protein to cotransform normal rat embryo cells with a mutant ras gene, induce foci in a Rat-1-derived cell line (Rat-1a), and localize in nuclei. Using the cotransformation assay, we found two regions of the protein (amino acids 105 to 143 and 321 to 439) where integrity was critical: one region (amino acids 1 to 104) that tolerated insertion and small deletion mutations, but not large deletions, and another region (amino acids 144) to 320) that was largely dispensable.

Prevention of tumorigenesis of oncogene-transformed rat fibroblasts with DNA site inhibitors of poly(ADP ribose) polymerase.

The EJ-ras gene was placed under the transcriptional control of the steroid-inducible mouse mammary tumor virus promoter/enhancer and introduced into Rat-1 fibroblasts, yielding the 14C cell line. When these cells were exposed to dexamethasone in vitro, EJ-ras mRNA was induced 15- to 20-fold, the cells grew in agar, and, after injection of cells into syngenic Fischer 344 rats, they produced lethal fibrosarcomas. Inhibitors of poly(ADP ribose) polymerase, which prevent the activation of the purified enzyme by a synthetic octadeoxyribonucleotide duplex, inhibited both in vivo tumorigenicity and in vitro growth in soft agar.

Hormonal regulation of the Rous sarcoma virus src gene via a heterologous promoter defines a threshold dose for cellular transformation.

We have derived rat cell lines producing different and regulatable amounts of pp60v-src by introducing the src gene of Rous sarcoma virus (RSV) under the control of the glucocorticoid-responsive transcriptional promoter from the mouse mammary tumor virus (MMTV). We find that the cellular phenotype is strictly dependent upon the dose of pp60v-src with a distinct threshold for changes indicative of neoplastic potential. Cells with low constitutive levels of pp60v-src are not phenotypically distinguishable from cells without v-src, but as little as a 4-fold increment in pp60v-src produces morphological transformation and anchorage-independent growth.