[Biosynthesis and secretion of collagen in normal and SV-40 virus-transformed human embryonal fibroblasts]

The biosynthesis and secretion of collagen proteins was studied in cultures of normal human embryo fibroblasts at different passages and growth stages as well as in cultures of human embryo fibroblasts transformed by oncogenic virus SV-40. It was found that normal fibroblasts maintain at a constant level the collagen synthesis throughout 20 passages, which is typical of proliferating and resting cells. Virus-transformed cells produce 3-4 times less collagen proteins on a per cell count. Normal and transformed fibroblasts do not differ in terms of total protein synthesis. Secretion of collagen and non-collagen proteins in transformed cell cultures appeared to be much lower than in normal cell cultures. Study of synthesized proteins by polyacrylamide gel electrophoresis showed that both types of cells secrete collagen proteins predominantly as polymers containing interchain S-S bonds of 3-helix molecules. Study of the protein-synthesizing activity of two polysomal fractions, i.e. membrane bound and free polysomes, isolated from the cells of both types in a cell-free system showed that membrane-bound polysomes from transformed fibroblasts synthesize collagen much less actively in comparison with normal cells. However, in transformed cells free polysomes, in contrast with normal cells, are active participants of a cell-free collagen protein synthesis.