We previously demonstrated that testicular zinc-finger protein (TZF) was a corepressor of the androgen receptor (AR). In the present study, We further showed that TZF-L, an alternative spliced variant of TZF, enhanced transactivation function of AR. Deletion analysis of TZF-L revealed that its N-terminus, which almost corresponded to that of TZF, but not its C-terminus was able to interact with AR. Additional analysis suggested that TZF kind TZF-L were able to Form both homodimers and heterodimers. TZF-L inhibited the homodimer formation of TZF and the intracellular dot formation of TZF. We propose that in the unique regulation system of AR-mediated transactivation, two spliced isoforms of TZF act as coactivator and corepressor, respectively. (c) 2006 Elsevier Inc. All rights reserved.