The importance of aberrant Bcl10 nuclear expression implicated in lymphomagenesis is becoming increasingly apparent. Our previous works indicate that Bcl10 can transactivate gene expression in yeast, nevertheless, little is known about the activities of nuclear Bcl10 in the mammalian cells and the mechanisms by which it modulates transcription. To understand it better, we mapped the location of the activation domain of Bcl10. This was done in the context of its interaction with TFIIB, as well as its ability to activate transcription as a fusion protein linked to the DNA-binding domain of Ga14 in the mammalian cells. Both approaches demonstrated that Bcl10 contains an activation domain in its N-terminal 13 amino acids. Together, these findings suggest that Bel 10 nuclear expression may modulate gene expression and Bcl10 is a potential transcriptional activator apart from its traditional roles that have been found. (C) 2004 Elsevier Inc. All rights reserved.