2634
To examine whether GATA-1 expression involves additional regulatory factors or is maintained entirely by an autoregulatory loop , we have used a transient heterokaryon system to test the ability of erythroid factors to activate the GATA-1 gene in nonerythroid nuclei .
 ( protein: GATA-1, None) , ( protein: GATA-1, None) , ( protein: regulatory factors, None) , ( DNA: GATA-1 gene, None) , ( protein: erythroid factors, 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: GATA-1, None) , ( protein: GATA-1, None) , ( protein: regulatory factors, None) , ( DNA: GATA-1 gene, None) , ( protein: erythroid factors, None) 