The deduced 257 amino acid protein PACRG (Parkin co-regulated gene) shows potential links to the ubiquitin/proteasome system. PACRG and Parkin are attached in a head-to-head arrangement on opposite DNA strands and share a common 5' flanking promoter region. The PACRG gene maps to chromosome 6q26; Northern blot analysis detects PACRG expression in all tissues examined except placenta. Using a positional cloning strategy in 197 Vietnamese leprosy simplex families (i.e. families with two unaffected parents and one affected child), significant connections between leprosy and 17 markers in the 5' regulatory region that PARK2 and PACRG share were observed. Possession of two or more of the 17 risk alleles is highly predictive of leprosy. PACRG is a gene located very close to parkin, in reverse orientation on the chromosome. It is thought to be co-transcribed with parkin by a bi-directional promoter between the two genes.