YY1 is a multifunctional transcription factor that activates or represses gene transcription depending on interactions with other regulatory proteins that include coactivator YY1AP. Here, we describe the cloning of a novel homolog of YY1AP, referred to as YARP, from the human neuroblastoma cell line SK-N-SH. The cloned cDNA encoded a 2240 amino acid protein that contained a domain which was 97% homologous to an entire YY1AP sequence of 739 amino acids. Two splice variants, YARP2 and YARP3, were also cloned. Northern blotting demonstrated the YARP mRNA (approximately 10 kb), which was increased 1.7-fold after dibutyryl cAMP-induced neural differentiation of the cells. Presence of YARP mRNA was also confirmed in human tissues such as the heart, brain and placenta. Bioinformatic analysis predicted various functional motifs in the YARP structure, including nuclear localization signals and domains associated with protein-protein interactions (PAH2), DNA-binding (SANT), and chromatin assembly (nucleoplasmin-like), outside the YY1AP-homology domain. Thus, we propose that YARP is multifunctional and plays not only a role analogous to YY1AP, but also its own specific roles in DNA-utilizing processes such as transcription.