InterPro domain: IPR003021

This family consists of the repair proteins Rad1, Rec1 and Rad17.

Rad1 is a component of the 9-1-1 cell-cycle checkpoint response complex (Rad9-Rad1-Hus1) that plays a major role in DNA repair [ 1 , 2 ]. Rad1 isoform 1 possesses 3'->5' double stranded DNA exonuclease activity [ 3 ].

Rec1 of Ustilago maydis plays a key role in regulating the genetic system of this fungus. Rec1 mutants are very sensitive to UV light. Mutation leads to a complex phenotype with alterations in DNA repair, recombination, mutagenesis, meiosis and cell division [ 4 ]. Rec1 shows 3'--5' exonuclease activity, but only in cells over-expressing Rec1.

Rad17 is a budding yeast checkpoint protein. It is a component of the checkpoint clamp complex (composed of Ddc1, Mec3 and Rad17) involved in the surveillance mechanism that allows the DNA repair pathways to act to restore the integrity of the DNA prior to DNA synthesis or separation of the replicated chromosomes [ 5 , 6 , 7 ]. The Ddc1-Mec3-Rad17 clamp complex shows no detectable exonuclease activity [ 8 ].

1. The human G2 checkpoint control protein hRAD9 is a nuclear phosphoprotein that forms complexes with hRAD1 and hHUS1. Mol. Biol. Cell 10, 1985-95
2. Physical interactions among human checkpoint control proteins HUS1p, RAD1p, and RAD9p, and implications for the regulation of cell cycle progression. Genomics 65, 24-33
3. A human homologue of the Schizosaccharomyces pombe rad1+ checkpoint gene encodes an exonuclease. J. Biol. Chem. 273, 18332-9
4. The REC1 gene of Ustilago maydis involved in the cellular response to DNA damage encodes an exonuclease. J. Biol. Chem. 269, 747-54
5. Cloning and characterization of RAD17, a gene controlling cell cycle responses to DNA damage in Saccharomyces cerevisiae. Nucleic Acids Res. 24, 1669-75
6. Yeast Rad17/Mec3/Ddc1: a sliding clamp for the DNA damage checkpoint. Proc. Natl. Acad. Sci. U.S.A. 100, 2249-54
7. Function of Rad17/Mec3/Ddc1 and its partial complexes in the DNA damage checkpoint. DNA Repair (Amst.) 4, 1189-94