Intracellular localization and DNA-binding properties of human papillomavirus type 18 E6 protein expressed with a baculovirus vector.

The E6 protein of human papillomavirus type 18 (HPV-18) is a putative zinc-finger protein that is expressed in HPV-18-induced genital neoplasias. We have studied the biochemical properties of E6 protein synthesized in large amounts with a baculovirus expression vector. When E6 protein was synthesized in insect cells infected with an E6-expressing baculovirus, the protein was localized to both nuclear and membrane fractions, with half-lives of 4 and 2 h, respectively. Changing the first five amino acids of E6 did not alter the pattern of cellular localization of the protein but dramatically increased the half-life of the nuclear component to longer than 30 h and increased the half-life of the membrane component to 8 h. Although the baculovirus-expressed E6 protein bound to double-stranded DNA with high affinity, no sequence specificity for HPV-18 DNA was detected.