A DAMAGE-RECOGNITION PROTEIN WHICH BINDS TO DNA CONTAINING INTERSTRAND CROSS-LINKS IS ABSENT OR DEFECTIVE IN FANCONI-ANEMIA, COMPLEMENTATION GROUP-A, CELLS

A DNA binding protein with specificity for DNA containing interstrand cross-links induced by 4,5',8-trimethylpsoralen (TMP) plus long wavele ngth ultraviolet (UVA) light has been identified in normal human chrom atin. Protein binding to DNA was determined using a gel mobility shift assay and an oligonucleotide containing a hot spot for formation of p soralen interstrand cross-links. Specificity of the damage-recognition protein for cross-links was demonstrated both by a positive correlati on between level of cross-link formation in DNA and extent of protein binding and by effective competition by treated but not undamaged DNA for the binding protein. Chromatin protein extracts from cells from in dividuals with the genetic disorder, Fanconi anemia, complementation g roup A (FA-A), which have decreased ability to repair damage produced by TMP plus UVA light, failed to show any protein binding to TMP plus UVA treated DNA. We have previously shown that these chromatin protein extracts contain a DNA endonuclease complex, pi 4.6, which specifical ly recognizes and incises DNA containing interstrand cross-links and w hich in FA-A cells is defective in its ability to incise this damaged DNA (Lambert et al. (1 992) Mutation Res., 273, 57 - 71). Together, th ese findings suggest that the DNA binding protein identified is involv ed in recognition and repair of DNA interstrand cross-links.