The chimeric tyrosine kinase p210 BCR ± ABL is involved in the pathogenesis of chronic myelogenous leukemia. It transforms immature hematopoietic cells in vitro and abrogates IL-3-dependent growth. The mechanisms by which p210 BCR ± ABL mediates its oncogenicity are not well elucidated. Identifying transcription factors targeted by the chimeric protein may help to clarify these mechanisms. We have analysed the eect of p210 BCR ± ABL expression on NF-kB activity in DA1 cells (an IL-3-dependent murine myeloid progenitor cell line). A speci®c stimulation of NF-kB activity by kinase-active wild-type p210 BCR ± ABL has been evidenced by transcriptional activation assays. Electrophoretic mobility supershift assays revealed the presence of p65 protein (RelA) DNA binding activity in p210 BCR ± ABL transformed DA1 cells but not in parental DA1 cells. Activation of RelA in transformed DA1 cells may occur by protein stabilization. Experiments using oligonucleotides antisense to RelA showed that p210 BCR ± ABL transfected cells failed to survive after IL-3 removal. Moreover, inhibition of cellular growth was shown following treatment of p210 BCR ± ABL transformed DA1 cells by p65 antisense oligonucleotides. This study suggests that p65 NF-kB may be an eector for p210 BCR ± ABL and probably contributes to its induced transformation process.

SUMMARYThirty-nine temperature-sensitive (ts) mutants that fail to grow at 39"5 °C but develop normally at 33 °C have been isolated from a nitrous-acid-treated stock of a wild-type strain of type 2 human adenovirus. The frequency of ts mutants among the surviving viruses was about IO %. Complementation tests in doubly infected cell cultures at restrictive temperature permitted the assignment of 19 of these mutants to I I complementation groups. They were characterized phenotypically according to their soluble capsid antigen production quantified by twodimensional immunoelectr0phoresis, virus DNA synthesis, as measured by alkaline sucrose gradient sedimentation of 34S DNA, and virion morphogenesis, as analysed by electron microscopy of cell sections. Two complementation groups were defective for DNA synthesis, four for soluble hexon production and two groups for total penton (penton base+fibre), while one group revealed no fibre production. Two complementation groups presented a normal antigen pattern, but the particles exhibited altered morphology as observed in cell sections.

Dimethyl-4,4'-dithiobisbutyrimidate dihydrochloride was used as a cleavable cross-linking reagent to maintain the structure of labile intermediates in adenovirus type 2 assembly. Analysis on sucrose gradients of nuclear adenovirus particles revealed two size classes, with sedimentation rates of 750 and 600S. After reversible fixation with diimido ester, the different classes were further separated on CsCl gradients and characterized with regard to their buoyant density, DNA content, and polypeptide composition. The 750S particles banded at 1.345 g/cm3 in CsCl, contained a DNA with a sedimentation coefficient of 34S in alkaline sucrose gradients, and had a polypeptide composition similar to that of young virions. The 600S population consisted of two types of particles with buoyant densities of 1.315 and 1.37 g/cm3. The 1.315-g/cm3 particles contained a DNA fragment of 7--11S and lacked the core proteins V and VII. In their place were found precursors P VI and P VIII and two nonvirion proteins with molecular weights of 50,000 (50K) and 39,000 (39K). 34S DNA was present in the 1.37-g/cm3 particles, which also lacked core proteins V and VII, as well as the 50K and 39K. Pulse-chase labeling kinetics suggested that the 1.315-g/cm3 particles were anterior to the 1.37-g/cm3 particles, themselves preceding the 1.345-g/cm3 young virions, and that the release of both 50K and 39K, possible scaffolding proteins, was required for entry of viral DNA.