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Displacement of an E-box-binding repressor by basic helix-loop-helix proteins : implications for B-cell specificity of the immunoglobulin heavy-chain enhancer .
 immunoglobulin heavy-chain enhancer, basic helix-loop-helix proteins, E-box-binding repressor
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 immunoglobulin heavy-chain enhancer, basic helix-loop-helix proteins, E-box-binding repressor