A novel member of the BTB/POZ family, PATZ, associates with the RNF4 RING finger protein and acts as a transcriptional repressor

We have identified a novel human gene encoding a 59-kDa POZ-AT hook-zinc fi nger protein (PATZ) that interacts with RNF4, a mediator of androgen recept or activity, and acts as a transcriptional repressor. PATZ cDNA was isolate d through a two-hybrid interaction screening using the RING finger protein RNF4 as a bait. In vitro and in vivo interaction between RNF4 and PATZ was demonstrated by protein-protein affinity chromatography and coimmunoprecipi tation experiments. Such interaction occurred through a small region of PAT Z containing an AT-hook DNA binding domain. Immunofluorescence staining and confocal microscopy showed that PATZ localizes in distinct punctate nuclea r regions and colocalizes with RNF4. Functional analysis was pe;formed by c otransfection assays: PATZ acted as a transcriptional repressor, whereas it s partner RNF4 behaved as a transcriptional activator. When both proteins w ere overexpressed a strong repression of the basal transcription was observ ed, indicating that the association of PATZ with RNF4 switches activation t o repression, In addition, RNF4 was also found to associate with HMGI(Y), a chromatin-modeling factor containing AT-hook domains.