The E7 oncoprotein encoded by human papillomavirus (HPV) type 16 repressed
the transcription of fibronectin, a key. component of the extracellular mat
rix. This repression, detected in several HPV-positive nontumorigenic and t
umorigenic cell lines, was abolished when the Cys-X-X-Cys repeats in E7 wer
e disrupted.