Genetic analysis of polyomavirus large T nuclear localization: nuclear localization is required for productive association with pRb family members.
AUTOR(ES)
Howes, S H
RESUMO
Polyomavirus large T antigen (LT) is a multifunctional nuclear protein. LT has two nuclear localization signals (NLS2), one spanning residues 189 to 195 (NLS1) and another spanning residues 280 to 286 (NLS2). Site-directed mutagenesis showed that each signal contains at least two critical residues. The possibility of connections between NLSs and adjacent phosphorylations has attracted much attention. Cytoplasmic LT (CyT) mutants were underphosphorylated, particularly at sites adjacent to NLS2. However, since a nuclear LT bearing an inactivated NLS2 was phosphorylated normally at adjacent sites, the signal was not directly required for phosphorylation. Conversely, LT could be translocated to the nucleus via NLS2 even when the adjacent phosphorylation sites were deleted. CyT was examined to probe the importance of LT localization. CyT was unable to perform LT functions related to interactions with retinoblastoma susceptibility gene (pRb) family members. Hence, CyT was unable to immortalize primary cells or to transactivate an E2F-responsive promoter. Consistent with these findings, CyT, though capable of binding pRb in vitro, did not cause relocalization of pRb in cells. Assays of transactivation of the simian virus 40 late promoter and of the human c-fos promoter showed that defects of CyT were not limited to functions dependent on pRb interactions.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=190233Documentos Relacionados
- Host range and cell cycle activation properties of polyomavirus large T-antigen mutants defective in pRB binding.
- The B-Domain Lysine Patch of pRB Is Required for Binding to Large T Antigen and Release of E2F by Phosphorylation
- Functional implications of mutations within polyomavirus large T antigen Rb-binding domain: effects on pRb and p107 binding in vitro and immortalization activity in vivo.
- The DnaJ domain of polyomavirus large T antigen is required to regulate Rb family tumor suppressor function.
- E1A promotes association between p300 and pRB in multimeric complexes required for normal biological activity.
