CHARACTERIZATION OF THE TRANSCRIPTIONAL REGULATOR YY1 - THE BIPARTITETRANSACTIVATION DOMAIN IS INDEPENDENT OF INTERACTION WITH THE TATA BOX-BINDING PROTEIN, TRANSCRIPTION FACTOR IIB, TAF(II)55, OR CAMP-RESPONSIVE ELEMENT-BINDING PROTEIN (CBP)-BINDING PROTEIN

YY1 is a multifunctional transcription factor implicated in both posit ive and negative regulation of gene expression as well as in initiatio n of transcription. We show that YY1 is ubiquitously expressed in grow ing, differentiated, and growth-arrested cells. The protein is phospho rylated and has a half life of 3.5 h. To define functional domains, we have generated a large panel of YY1 mutant proteins. These were used to define precisely the DNA-binding domain, the region responsible for nuclear localization, and the transactivation domain. The two acidic domains at the N terminus each provide about half of the transcription al activating activity. Furthermore, the spacer region between the Gly /Ala-rich and zinc finger domains has accessory function in transactiv ation. YY1 has been shown previously to bind to TAF(II)55, TATA box bi nding protein, transcription factor IIB, and p300. In addition, we ide ntified cAMP-responsive element-binding protein (CBP) binding protein as a YY1 binding partner. Surprisingly, these proteins did not bind to the domains involved in transactivation, but rather to the zinc finge r and Gly/Ala-rich domains of YY1. Thus, these proteins do not explain the transcriptional activating activity of YY1, but rather may be inv olved in repression or in initiation.