Identification of the nuclear localization and export signals of high risk HPV16 E7 oncoprotein
- Biology Department, Boston College, Higgins Hall, Room 578, 140 Commonwealth Avenue, Chestnut Hill, MA 02467 (United States)
The E7 oncoprotein of high risk human papillomavirus type 16 (HPV16) binds and inactivates the retinoblastoma (RB) family of proteins. Our previous studies suggested that HPV16 E7 enters the nucleus via a novel Ran-dependent pathway independent of the nuclear import receptors (Angeline, M., Merle, E., and Moroianu, J. (2003). The E7 oncoprotein of high-risk human papillomavirus type 16 enters the nucleus via a nonclassical Ran-dependent pathway. Virology 317(1), 13-23.). Here, analysis of the localization of specific E7 mutants revealed that the nuclear localization of E7 is independent of its interaction with pRB or of its phosphorylation by CKII. Fluorescence microscopy analysis of enhanced green fluorescent protein (EGFP) and 2xEGFP fusions with E7 and E7 domains in HeLa cells revealed that E7 contains a novel nuclear localization signal (NLS) in the N-terminal domain (aa 1-37). Interestingly, treatment of transfected HeLa cells with two specific nuclear export inhibitors, Leptomycin B and ratjadone, changed the localization of 2xEGFP-E7{sub 38-98} from cytoplasmic to mostly nuclear. These data suggest the presence of a leucine-rich nuclear export signal (NES) and a second NLS in the C-terminal domain of E7 (aa 38-98). Mutagenesis of critical amino acids in the putative NES sequence ({sub 76}IRTLEDLLM{sub 84}) changed the localization of 2xEGFP-E7{sub 38-98} from cytoplasmic to mostly nuclear suggesting that this is a functional NES. The presence of both NLSs and an NES suggests that HPV16 E7 shuttles between the cytoplasm and nucleus which is consistent with E7 having functions in both of these cell compartments.
- OSTI ID:
- 21182792
- Journal Information:
- Virology, Vol. 383, Issue 1; Other Information: DOI: 10.1016/j.virol.2008.09.037; PII: S0042-6822(08)00627-2; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0042-6822
- Country of Publication:
- United States
- Language:
- English
Similar Records
The nuclear localization of low risk HPV11 E7 protein mediated by its zinc binding domain is independent of nuclear import receptors
High levels of p105 (NFKB1) and p100 (NFKB2) proteins in HPV16-transformed keratinocytes: role of E6 and E7 oncoproteins