12547
The 5'-positive regulatory unit , consisting of the promoter and the 5' enhancer , is already active at the CD4 - CD8 -double-negative (DN) stage of development.
 5' enhancer, 5'-positive regulatory unit, promoter, CD4, CD8
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:
 5' enhancer, 5'-positive regulatory unit, promoter, CD4, CD8