EARLY B-CELL FACTOR BINDS TO A SITE CRITICAL FOR LAMBDA-5 CORE ENHANCER ACTIVITY

The pre-B cell-specific expression of the lambda 5 gene is regulated a t the level of transcription. The 5' region of the lambda 5 gene has b een shown to contain an enhancer that activates heterologous promoters . Here, we show that this enhancer, B-lambda 5, also acts as a lineage - and tissue-restricted enhancer on its own promoter. We define the en hancer core, b(lambda 5), that carries around 50% of the total enhance r activity. We also demonstrate that the transcription factor early B cell factor (EBF) binds to a DNA motif in the lambda 5 core enhancer w hich is crucial for enhancer activity, suggesting that lambda 5 is a s econd target gene of EBF.