title: Entry of exogenous polypeptides into the nucleus of living cells: facts and speculations.
abstract: Although the plasma membrane acts as an impermeable barrier to most macromolecules, some exogenous proteins (for example fibroblast growth factor, HIV-1 Tat and lactoferrin) can gain access into the cytosol and reach the nucleus of living cells. How are these exogenous polypeptides selected over and above other extracellular proteins? How and where do they cross the cell membrane? Why do cells need to take up exogenous transcription factors when sophisticated signal-transduction pathways are available? Here, we review the current knowledge on these issues and discuss some mechanistic and physiological implications of this unconventional and direct way of taking messages to the nucleus.
authors.affiliation: Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Rubartelli
authors.forename: R
authors.initials: R
authors.lastname: Sitia