Expression of the potential novel gene E6DG1 downregulated by the E6 protein of human papillomavirus type 16 is correlated with anchorage-independent growth

A novel gene transcript that is downregulated by HPV16 E6 protein was identified in mouse cells using differential hybridization and designated E6DGI. The cloned cDNA of E6DGI was 1.3 kb in length and contained a small ORF potentially encoding a polypeptide of 45 amino acids. In vitro transcription and translation of E6DG1 cDNA resulted in a product of approximately 7 kDa and Western blot analysis using antibodies for E6DG1 peptide detected 7 and 14 kDa proteins. Downregulation of E6DGI mRNA levels in cells expressing HPV16 E6 protein was observed at subconfluent cell densities, but not in confluent cells. Repression of E6DG1 protein enhanced the anchorage-independent growth and weakened the cell adhesion in Panc1 cells. Immunofluorescence analysis revealed the localization of E6DG1 within the nucleus. These results indicate that the E6DG1 protein may function in a signaling pathway related to anchorage-independent growth and adhesion control.