In a chicken B cell line, DT40, the disruption of HDAC2 (chHDAC2) gene causes an alteration of several gene expressions including chicken IgM light chain (chIgM-L) gene by 2D-PAGE analysis. To investigate the transcriptional function of chHDAC2, we employed the chIgM-L promoter reporter plasmid. We found that chHDAC2 represses activated chIgM-L promoter activity. In transient expression experiments in NIH 3T3 cell. the specific histone deacetylase inhibitor tricostatin A (TSA) increased transactivation of chIgM-L promoter activity mediated by chicken Oct-1 and OBF-1 proteins. In transient coexpression of the three class I chicken histone deacetylases (chHDAC1-3) tested, only chHDAC2 repressed the activated chIgM-L promoter activity. These findings suggest that chHDAC2 might be recruited to the chIgM-L promoter and specifically repress chIgM-L transcription. (C) 2002 Elsevier Science (USA). All rights reserved.