MC29 virus-coded protein occurs as monomers and dimers in transformed cells.

The MC29 virus-coded protein p110gag-myc was found exclusively in the nucleus of transformed Japanese quail (Q8) cells, and time course experiments indicated that the protein had a half-life of about 30 min. When extracts of either Q8 or chicken embryo cells infected with MC29 virus were prepared with nondenaturing detergents and then sedimented in sucrose gradients, p110 was found in the fractions expected to contain monomers (5.9S), dimers (9.3S), or mixtures of the two. The same extracts treated with denaturing detergent (0.2% sodium dodecyl sulfate) exhibited p110 only in fractions expected for the monomeric protein, but beta-mercaptoethanol had no effect on the original distribution. Gradients prepared with 0.5 or 1.0 M NaCl failed to dissociate the faster-sedimenting form. No other protein or polyribonucleotide which could increase the sedimentation rate of p110 was found, and neither RNase nor DNase altered the sedimentation pattern of p110 in nondenatured extracts. A reassociation of monomeric p110 into dimers discernible by gel electrophoresis was demonstrated.