The MarFinder algorithm was applied to a newly sequenced segment of 16p13.13 abutting the 3′ end of the human PRM1 → PRM2 → TNP2 locus. A candidate region of matrix attached was identified. Subsequent biophysical analysis showed that this region was attached to the somatic nuclear matrix. Nucleotide sequence analysis also revealed the presence of a CpG island. Data base queries showed that this region contained the SOCS-1 gene. Thus, the SOCS-1 gene is bounded by a somatic MAR and is just 3′ of the spermatid-expressed PRM1 → PRM2 → TNP2 domain at position 16p13.13.