CHROMOSOMAL LOCALIZATION OF 3 REPAIR GENES - THE XERODERMA-PIGMENTOSUM GROUP-C GENE AND 2 HUMAN HOMOLOGS OF YEAST RAD23

The nucleotide excision repair (NER) disorder xeroderma pigmentosum (X P) is characterized by sun (UV) sensitivity, predisposition to skin ca ncer, and extensive genetic heterogeneity. Recently, we reported the c loning and analysis of three human NER genes, XPC, HHR23A, and HHR23B. The previously cloned XPC gene is involved in the common XP complemen tation group C, which is defective in excision repair of nontranscribe d sequences in the genome. The XPC protein was found to be complexed w ith the product of HHR23B, one of the two human homologs of the Saccha romyces cerevisiae NER gene RAD23. Here we present the chromosomal loc alization by in situ hybridization using haptenized probes of all thre e genes. The HHR23A gene was assigned to chromosome 19p13.2. Interesti ngly, the HHR23B and XPC genes, the product of which forms a tight com plex, were found to colocalize on band 3p25.1, Pulsed-field gel electr ophoresis revealed that the HHR23B and XPC genes possibly share a MluI restriction fragment of about 625 kb. Potential involvement of the HH R23 genes ih human genetic disorders is discussed. (C) 1994 Academic P ress, Inc.