1021
Expression of the kappa immunoglobulin light chain gene requires developmental- and tissue-specific regulation by trans-acting factors which interact with two distinct enhancer elements .
 enhancer elements, trans-acting factors, kappa immunoglobulin light chain gene
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:
 enhancer elements, trans-acting factors, kappa immunoglobulin light chain gene