Kin17 is a human Zinc-finger protein presenting an intranuclear foci distribution in proliferating cells. These focal structures are associated with cell proliferation and unrepaired DNA lesions. This evolutionarily conserved DNA-binding protein was initially identified because it cross-reacts with antibodies raised against Escherichia coli RecA protein. Ionizing radiation, ultraviolet light, and chemical genotoxics (like bleomycine) enhance KIN17 gene expression. Certain carcinoma cell lines spontaneously upregulate kin17 protein, suggesting that increased expression levels may be a consequence of the immortalized phenotype. Accordingly, human cells immortalized with Simian Virus 40 overexpress endogenous kin17 protein, which colocalizes with SV40 large T-antigen in nucleoplasmic foci. Kin17 protein physicaly interacts with T-antigen through the region which allows the interaction with p53 and DNA polymerase &agr;. The overexpression of kin17 protein in vivo and the introduction of human kin17 protein in an in vitro assay reduce T-antigen-dependent DNA replication. The data indicate that kin17 protein may be involved in DNA replication in human cells and suggest that it may contribute to the process of carcinogenesis. For details, see the article by Miccoli et al. on page 5425 of this issue.