Constitutive expression of FosB and its short form, FosB/SF, induces malignant cell transformation in rat-1A cells

We have established Rat-1A cell lines constitutively expressing c-Fos and the two products of the fosB gene, FosB and its short form, FosB/SF. The expressed proteins in the different stable transfectants have been characterized by immunofluorescence and immunoprecipitation analysis. Our results demonstrate that constitutive expression of FosB, like the constitutive expression of c-Fos and, to a lesser extent, FosB/SF, results in cells that grow to increased saturation densities and have the ability to grow in an anchorage-independent manner. Most important is the finding that expression of these proteins augments the tumorigenic potential of Rat-1A cells. These results show that both forms of FosB have a stimulatory effect on cell proliferation.     

Structure and potential C-terminal dimerization of a recombinant mutant of surfactant-associated protein C in chloroform/methanol.

The solution structure of a recombinant mutant [rSP-C (FFI)] of the human surfactant-associated protein C (hSP-C) in a mixture of chloroform and methanol was determined by high-resolution NMR spectroscopy. rSP-C (FFI) contains a helix from Phe5 to the C-terminal Leu34 and is thus longer by two residues than the helix of porcine SP-C (pSP-C), which is reported to start at Val7 in the same solvent. Two sets of resonances at the C-terminus of the peptide were observed, which are explained by low-order oligomerization, probably dimerization of rSP-C (FFI) in its alpha-helical form. The dimerization may be induced by hydrogen bonding of the C-terminal carboxylic groups or by the strictly conserved C-terminal heptapeptide segment with a motif similar to the GxxxG dimerization motif of glycophorin A. Dimerization at the heptapeptide segment would be consistent with findings based on electrospray ionization MS data, chemical cross-linking studies, and CNBr cleavage data.