Mapping by in vitro constructs of the P100gag-mil region, accounting for induction of chicken neuroretina cell proliferation

Efficacy of adenoviral TNF alpha antisense is enhanced by a macrophage specific promoter

Macrophage-derived TNF alpha is a critical mediator of inflammation and destruction in diseases such as rheumatoid arthritis and Crohn's disease. These studies were undertaken to develop an effective adenovirus-based strategy to specifically suppress TNF alpha in primary human macrophages. A variety of promoters and LTRs were evaluated for effective expression in the macrophage cell line RAW 264.7. The CMV promoter and the Visna LTR were the most strongly expressed and were therefore used to drive the expression of TNF alpha antisense fragments. In transient transfection assays, the antisense fragment terminating at the 3' end of the first exon (216 bp) was superior to the others (70 and 750 bp), when expressed under the control of either the CMV promoter or the Visna LTR. Adenoviral vectors expressing the 216 bp TNF alpha antisense fragment, controlled by the CMV promoter or the Visna LTR, were both effective at suppressing LPS-induced TNF alpha secretion by primary human macrophages. However, the Visna LTR was more effective not only at suppressing LPS-induced TNF alpha secretion, but also IL-6, which is highly sensitive to TNF alpha secretion. These results demonstrate that effective, specific, suppression of TNF alpha in macrophages is possible, employing a directed antisense approach and a promoter system that is highly efficient in human macrophages.

Definition of functional domains in P135gag-myb-ets and p48v-myb proteins required to maintain the response of neuroretina cells to basic fibroblast growth factor

The v-myb- and v-ets-containing E26 retrovirus induces the proliferation of chicken neuroretina (CNR) cells in minimal medium. Proliferation of E26 CNR cells is strongly stimulated by basic fibroblast growth factor (bFGF). The v-myb-containing avian myeloblastosis virus also induces the proliferation of infected CNR cells stimulated by bFGF. Both E26 CNR and avian myeloblastosis virus CNR cells are able to form colonies in soft agar in the presence of bFGF. This suggests that the v-myb product, a nuclear sequence-specific DNA-binding protein which activates gene expression in transient transfection assays, plays a role in the proliferative response of the infected CNR cells. To determine the structure-function relationships of P135gag-myb-ets and p48v-myb, we have used deletion mutants expressed in retroviral vectors and have analyzed their effect on CNR cell proliferation as well as their effect on the CNR cell response to bFGF. We show that v-ets is not required for bFGF stimulation but increases the proliferation of CNR cells in minimal medium. In the v-myb mutants, the gag sequences derived from the helper virus increase the potency of the myb gene. The carboxyl-terminal domain required for the growth and transformation of myeloid cells and needed for maximal trans-activation in transient DNA transfection assays in fibroblasts was not required for the growth and bFGF response of CNR cells. In contrast, the domain encompassing amino acids 240 to 301 (containing part of the transcriptional activation domain of v-myb) was absolutely required for the response of CNR cells to bFGF and could be functionally replaced by the carboxyl-terminal transcriptional activation domain of the VP16 protein of herpes simplex virus.

Role of gag sequence in the biochemical properties and transforming activity of the avian sarcoma virus UR2-encoded gag-ros fusion protein

The transforming protein P68gag-ros of avian sarcoma virus UR2 is a transmembrane tyrosine protein kinase molecule with the gag portion protruding extracellularly. To investigate the role of the gag moiety in the biochemical properties and biological functions of the P68gag-ros fusion protein, retroviruses containing the ros coding sequence of UR2 were constructed and analyzed. The gag-free ros protein was expressed from one of the mutant retroviruses at a level 10 to 50% of that of the wild-type UR2. However, the gag-free ros-containing viruses were not able to either transform chicken embryo fibroblasts or induce tumors in chickens. The specific tyrosine protein kinase activity of gag-free ros protein is about 10- to 20-fold reduced as judged by in vitro autophosphorylation. The gag-free ros protein is still capable of associating with membrane fractions including the plasma membrane, indicating that sequences essential for recognition and binding membranes must be located within ros. Upon passages of the gag-free mutants, transforming and tumorigenic variants occasionally emerged. The variants were found to have regained the gag sequence fused to the 5' end of the ros, apparently via recombination with the helper virus or through intramolecular recombination between ros and upstream gag sequences in the same virus construct. All three variants analyzed code for gag-ros fusion protein larger than 68 kDa. The gag-ros recombination junction of one of the transforming variants was sequenced and found to consist of a p19-p10-p27-ros fusion sequence. We conclude that the gag sequence is essential for the transforming activity of P68gag-ros but is not important for its membrane association.

Two nuclear oncogenic proteins, P135gag-myb-ets and p61/63myc, cooperate to induce transformation of chicken neuroretina cells

Several studies have shown that full transformation of primary rodent fibroblasts can be achieved in vitro through the cooperation of two oncogenes (usually one nuclear and one cytoplasmic) classified on the basis of different complementation groups. We have shown previously that cooperation between v-mil (cytoplasmic, serine-threonine kinase product), and v-myc (nuclear, DNA-binding product) is required to transform 7-day-old chicken neuroretina cells, which in usual culture medium do not rapidly proliferate. v-mil induces sustained growth of chicken neuroretina cells without transformation; v-myc fails to stimulate the proliferation of chicken neuroretina cells but is required to achieve transformation of the proliferating cells. Here, we present results indicating that the P135gag-myb-ets nuclear protein of avian erythroblastosis virus E26 is able to induce proliferation but not transformation of chicken neuroretina cells. v-myc is required in addition to P135gag-myb-ets to achieve chicken neuroretina cell transformation. In contrast, we found that the P135gag-myb-ets and P100gag-mil proteins are not able to cooperate in this system.