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Compartments and Information Flow between
Nucleus & CytoplasmLecture 18 BSCI 420/421 Oct 14, 2002
“Your future is ahead of you” - Yogi Berra
1. Compartments of Eukaryotic cells
2. Information flow between Nucleus and cytoplasm
Molecules smaller than 9 nm or 60 KDa can enter nuclei by passive diffusion thru pores.Larger must have Nuclear Localization Signals (NLS) and be actively transported in.
Importance of NLS SV40 T-antigenWith normal orMutant NLS in infected cells.T-antigen detected by fluorAnti-T
The cycle of Ran, a monomeric G protein, gives directionality to nuclear import and export . Ran GTPase activating proteinIs cytosolic and Ran Guanine nucleotide exchange factor isNuclear.
Nuclear transport of Dorsal TF protein determines ventral cellsFrom dorsal cells in Drosophila embryos
Toll cell surface receptors areActivated by ventral signals,which leads to phosphorylation of an Inhibitor , cactus. This causes cactus to bedegraded, exposing the NLSon Dorsal, which enters the nucleus.