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

Compartments of a eukaryotic cell

Compartments of an animal cell

Flow chart of Eukaryotic cell

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.

Structure of Ran-GTP & How its binding to import receptor leads to release of cargo protein

Nuclear import and export depend on receptors& Ran cycle

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.