Cellular radiosensitivity in V79 cells is linked to alterations in chromatin structure

V79 cells grown as spheroids are more radioresistant than those grown as monolayers. Viable cells from spheroid culture contain restraints to ethidium bromide driven rewinding of DNA supercoils that are absent in monolayer cells. Spheroid cells also contain a DNA-protein matrix that is more resistant to detergent-induced degradation. The increase in structural integrity may be related to a 55-60 kD protein in the nucleoids of spheroid, but not monolayer cells. Spheroid cell radioresistance may therefore be related to a more stable chromatin platform for high fidelity repair of DNA damage.