9622
Site - directed mutagenesis of binding sites for the repressor proteins BP1 and BP2 in the upstream portion of the beta globin gene flanking region led to a 4 - 6 fold increase in promoter activity .
 repressor proteins BP1, BP2, beta globin gene flanking region
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 repressor proteins BP1, BP2, beta globin gene flanking region