This domain is called PHR as it was original found in the proteins PAM (Swiss:O75592), highwire (Swiss:Q9NB71) and RPM (Swiss:Q17551) [1]. This domain can be duplicated in the highwire, PFAM and PRM sequence. The C-terminal region of the protein BTBD1 includes the PHR domain and is known to interact with Topoisomerase I, an enzyme which relaxes DNA supercoils [2].

1: BTBD1 and BTBD2 colocalize to cytoplasmic bodies with the RBCC/tripartite motif protein, TRIM5delta. Xu L, Yang L, Moitra PK, Hashimoto K, Rallabhandi P, Kaul S, Meroni G, Jensen JP, Weissman AM, D'Arpa P; Exp Cell Res 2003;288:84-93. PMID:12878161

2: Characterization of BTBD1 and BTBD2, two similar BTB-domain-containing Kelch-like proteins that interact with Topoisomerase I. Xu L, Yang L, Hashimoto K, Anderson M, Kohlhagen G, Pommier Y, D'Arpa P; BMC Genomics 2002;3:1. PMID:11818025