THE NUCLEAR CONCENTRATION OF KIN17, A MOUSE PROTEIN THAT BINDS TO CURVED DNA, INCREASES DURING CELL-PROLIFERATION AND AFTER UV IRRADIATION

UV-irradiation induces, in mammalian cells, the expression of a set of genes known as the 'UV-response', which may be reminiscent of the bac terial response, called SOS system, The multifunctional protein RecA c ontrols the expression of the SOS genes. We report the expression prof ile of a mouse gene conserved among mammals, called Kin17, that codes a DNA-binding protein of undetermined biochemical activity and which s hares epitopes with the bacterial RecA protein. We demonstrate that th e level of Kin17 RNA was 5-fold higher in mid-S phase of serum-stimula ted BALB/c 3T3 fibroblasts than in quiescent cells, Cells in S-phase d isplayed a high level of kin17 protein with a marked nuclear localisat ion. The maximal level of Kin17 RNA was observed 18 h after serum stim ulation, indicating that Kin17 gene is a new member of the late growth -related genes. The accumulation of kin17 protein during cell prolifer ation follows the increase in Kin17 RNA and correlates with DNA synthe sis, which suggests a possible role of kin17 protein in a transaction related to DNA-replication, In quiescent fibroblasts, a 3-fold increas e in Kin17 RNA was seen 13 h after UV irradiation, In parallel, kin17 protein accumulated in the nucleus, which suggests that it might be re quired after the stress produced by UV irradiation.