tokens: Transient transfection studies in MLA-144 T cells revealed that constructs containing mutations in the AP-1 site almost completely abolished CAT activity while mutation of the Elf-1 site or the NF-IL-3 site , a previously described nuclear protein binding site ( bp. -155 to -148 ) in the IL-3 promoter , reduced CAT activity to < 25 % of the activity given by wild-type constructs .