13473
Truncation of the beta globin promoter led to a 2-3 fold increase in promoter activity .
 ( DNA: beta globin promoter, 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:
 ( DNA: beta globin promoter, None) 