Early B cell factor binds to a site critical for lambda5 core enhancer activity.

The pre-B cell-specific expression of the lambda5 gene is regulated at the level of transcription. The 5' region of the lambda5 gene has been shown to contain an enhancer that activates heterologous promoters. Here, we show that this enhancer, B(lambda5), also acts as a lineage- and tissue-restricted enhancer on its own promoter. We define the enhancer core, b(lambda5), that carries around 50% of the total enhancer activity. We also demonstrate that the transcription factor early B cell factor (EBF) binds to a DNA motif in the lambda5 core enhancer which is crucial for enhancer activity, suggesting that lambda5 is a second target gene of EBF.