passages.id: split_8_test_654_passage
passages.type: progene_text
passages.text: The estrogen receptor ( ER ) protein enhanced Sp1 interactions with upstream GC - rich sites , and interactions of ER , Sp1 , and ER / Sp1 with downstream DNA bound - NF-Y was investigated by kinetic analysis for protein - DNA binding ( on - and off - rates ) , coimmunoprecipitation , and pulldown assays using wild - type and truncated glutathione S-transferase ( GST ) - Sp1 chimeric proteins .