ZF5, which is a Kruppel-type transcriptional repressor, requires the zinc finger domain for self-association

ZF5, which we have cloned as a transcriptional repressor on the mouse c-myc promoter, has the POZ domain at the amino-terminus and the Kruppel-type zi nc finger domain at the carboxy-terminus, In this report, we showed that ZF 5 has two contradictory functions in transcription: activation of human imm unodeficiency virus (HIV) promoter and repression of the HSV thymidine kina se (TK) promoter. The POZ domain contributed to the repressor activity, whe reas the active function resulted from the DNA-binding ability of the zinc finger domain. We demonstrated that the POZ domain has a function mediating homo-meric protein-protein interaction and this interaction requires the z inc finger domain. Furthermore, the POZ domain decreased the DNA-binding ac tivity of the zinc finger domain. These results can provide evidence indica ting the important interaction between the POZ and zinc finger domains. (C) 1999 Academic Press.