InterPro domain: IPR011333

The BTB (for BR-C, ttk and bab) [ 1 ] or POZ (for Pox virus and Zinc finger) [ 2 , 3 ] domain is a versatile protein-protein interaction motif involved in many cellular functions, including transcriptional regulation, cytoskeleton dynamics, ion channel assembly and gating, and targeting proteins for ubiquitination [ 4 ]. The BTB domain can occur alongside other domains: BTB-zinc finger (BTB-ZF), BTB-BACK-Kelch (BBK), voltage-gated potassium channel T1 (T1-Kv) [ 5 ], MATH-BTB, BTB-NPH3 and BTB-BACK-PHR (BBP). Other proteins, such as Skp1 and ElonginC, consist almost exclusively of the core BTB fold. In all of these protein families, the BTB core fold is structurally conserved, consisting of a 2-layer alpha/beta topology where a cluster of alpha helices is flanked by short beta-sheets [ 6 ]. POZ domains from several zinc finger proteins have been shown to mediate transcriptional repression and to interact with components of histone deacetylase co-repressor complexes including N-CoR and SMRT [ 7 , 8 , 9 ]. The POZ or BTB domain is also known as BR-C/Ttk or ZiN.

This entry includes the BTB/POZ domain, as well as Skp1 N-terminal region which has an alpha/beta structure similar to that of the BTB/POZ domain fold [ 10 , 10 ].

1. The BTB domain, found primarily in zinc finger proteins, defines an evolutionarily conserved family that includes several developmentally regulated genes in Drosophila. Proc. Natl. Acad. Sci. U.S.A. 91, 10717-21
2. The POZ domain: a conserved protein-protein interaction motif. Genes Dev. 8, 1664-77
3. Functional analysis of the role of POK transcriptional repressors. J. Mol. Biol. 6, 8-18
4. Sequence and structural analysis of BTB domain proteins. Genome Biol. 6, R82
5. Fold prediction and evolutionary analysis of the POZ domain: structural and evolutionary relationship with the potassium channel tetramerization domain. null 285, 1353-61
6. Crystal structure of the BTB domain from PLZF. Proc. Natl. Acad. Sci. U.S.A. 95, 12123-8
7. The LAZ3/BCL6 oncogene encodes a sequence-specific transcriptional inhibitor: a novel function for the BTB/POZ domain as an autonomous repressing domain. Cell Growth Differ. 6, 1495-503
8. The BCL-6 POZ domain and other POZ domains interact with the co-repressors N-CoR and SMRT. Oncogene 17, 2473-84
9. Components of the SMRT corepressor complex exhibit distinctive interactions with the POZ domain oncoproteins PLZF, PLZF-RARalpha, and BCL-6. J. Biol. Chem. 273, 27695-702
10. Insights into SCF ubiquitin ligases from the structure of the Skp1-Skp2 complex. Nature 408, 381-6