LTR -directed transcription was measured by using luciferase reporter constructs that were transiently transfected into cultured cells .
ltr -directed transcription was measured by using luciferase reporter constructs that were transiently transfected into cultured cells .
B-DNA_domain_or_region O O O O O O B-DNA_family_or_group I-DNA_family_or_group I-DNA_family_or_group O O O O O B-cell_line I-cell_line O