1459
Because inhibition of DNA-binding activity is associated with increasing intracellular glutathione disulfide levels and GSSG can be shown to inhibit the DNA-binding activity directly in cell-free systems , our studies suggest that GSSG is a physiologically relevant inhibitor in intact cells also.
 GSSG, GSSG, intact cells
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:
 GSSG, GSSG, intact cells