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 .
 ( protein: c-Myc, None) , ( protein: YY1, None) , ( protein: CXCR4, None) , ( protein: USF/ c-Myc, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: c-Myc, None) , ( protein: YY1, None) , ( protein: CXCR4, None) , ( protein: USF/ c-Myc, None) 