6990
In this study, we show that USF/ c-Myc up-regulates, while YY1 down-regulates the promoter activity of CXCR4 , a coreceptor for T cell-tropic HIV-1 entry .
 c-Myc, YY1, CXCR4, USF/ c-Myc
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:
 c-Myc, YY1, CXCR4, USF/ c-Myc