PMID-sentid Pub_year Sent_text comp_official_name comp_offsetprotein_name organism prot_offset 7969153-3 1994 To further understand the roles of E2F in the cell cycle progression, we have overexpressed exogenous E2F-1 by using a tetracycline-controlled expression system. Tetracycline 119-131 E2F transcription factor 1 L homeolog Xenopus laevis 102-107