English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

It has been extensively demonstrated that growth factors play a key role in the regulation of proliferation. Several lines of evidence support the hypothesis that for the induction of cell cycle progression in the absence of exogenous growth factors, oncogenes must either induce autocrine growth factor secretion or, alternatively, activate their receptors or their receptor substrates. Cells expressing polyomavirus large T antigen (PyLT) display reduced growth factor requirements, but the mechanisms underlying this phenomenon have yet to be explored. We conducted tests to see whether the reduction in growth factor requirements induced by PyLT was related to alterations of growth factor-dependent signals. To this end, we analyzed the phosphorylation status of a universal tyrosine kinase substrate, the transforming Shc adapter protein, in fibroblasts expressing the viral oncogene. We report that the level of Shc phosphorylation does not decrease in PyLT-expressing fibroblasts after growth factor withdrawal and that this PyLT-mediated effect does not require interaction with protein encoded by the retinoblastoma susceptibility gene. We also found that the chronic activation of the adapter protein is correlated with the binding of Shc to Grb-2 and with defects in the downregulation of mitogen-activated protein kinases. In fibroblasts expressing the nuclear oncoprotein, we also observed the formation of a PyLT-Shc complex that might be involved in constitutive phosphorylation of the adapter protein. Viewed comprehensively, these results suggest that the cell cycle progression induced by PyLT may depend not only on the direct inactivation of nuclear antioncogene products but also on the indirect induction, through the alteration of cytoplasmic pathways, of growth factor-dependent nuclear signals.

Polyomavirus Large T Antigen Induces Alterations in Cytoplasmic Signalling Pathways Involving Shc Activation