Putative regulatory sequence in human papillomavirus type 16 E2 open reading frame

A 114 bp fragment of the human papillomavirus type 16 (HPV16) E2 open reading frame (nt. 3142-3255) containing a putative estrogen responsive element (ERE) was amplified and cloned into pBLCAT2 plasmid in both sense (p159-4) and anti-sense (p164) orientation. The plasmids were transfected into human breast-cancer cell line MCF-7 containing estrogen receptor and the cultures were kept in the presence or absence of beta-estradiol. The chloramphenicol acetyltransferase (CAT) activity was not influenced by estrogen. However, a silencer effect was observed both in cultures transfected with p159-4 and p164 plasmids. We prepared and cloned synthetic fragments containing the putative ERE and failed to prove that the palindrome in the putative ERE was responsible for the silencer activity.