5903
Retinoic acid can directly modulate gene expression via binding to its nuclear receptors , which can, in turn, activate transcription of target genes .
 target genes, nuclear receptors
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:
 target genes, nuclear receptors