Androgen/androgen receptor (AR) signaling plays decisive roles in testicular spermatogenesis [1].However,the underlying molecular mechanism of androgen and AR regulation (i.e.the genes that are regulated and their functions) remains largely undefined.Microarray analysis combined with androgen treatment or AR knockout animal models has identified androgen-dependent genes in mouse testis [2,3].However,this approach does not distinguish direct and indirect targets of androgen/AR.Until now,only a few AR-binding sites containing androgen responsive elements (AREs) located within the promoter regions of androgen responsive genes in testis have been reported,implying that these genes are direct targets of AR.These genes include kallikrein 27 (Klk27) [4],reproductive homeobox 5 (Rhox5) [5],epididymal peptidase inhibitor (Eppin) [6],and cytochrome P450,family 17,subfamily a,polypeptide 1 (Cypl7) [7].All of these binding events were demonstrated using in vitro assays including electrophoretic mobility shift assays (EMSA),deoxyribonuclease I footprinting,and luciferase assays.However,these in vitro measurements cannot be easily extrapolated into in vivo mechanisms,as mammalian genes are commonly organized into broad chromosomal domains,and such domains cannot be readily reconstituted in vitro.Thus the in vivo assays are greatly required for measuring AR-DNA interactions in testis and understanding the physiological transcriptional mechanisms.Until now,only one AR-binding site associated with tubulin,beta 3 class Ⅲ (Tubb3) gene was identified in mouse testis in vivo using chromatin immunoprecipitation (ChIP) [8].