Chapter 10 Flashcards
________________: separates the nuclear contents from the cytoplasm
it controls traffic of ___________ through nuclear pore complexes, and plays a critical role in regulating gene expression
the nuclear envelope consists of 1) _______________2) and underlying____________ 3)____________. outer membrane is continuous with the ________________. Inner membrane has proteins that bind the nuclear ___________-
NUCLEAR ENVELOPE: separates the nuclear contents from the cytoplasm. It controls traffic of PROTEINS AND RNAs through nuclear pore complexes, and plays a critical role in regulating gene expression
The nuclear envelope consists of 1)two NUCLEAR MEMBRANE, 2) an underlying NUCLEAR LAMINA, 3) NUCLEAR PORE COMPLEX. Outer membrane is continuous with the ENDOPLASMIC RECTICULUM. inner membrane has proteins that bind the nuclear LAMINA
nuclear membrane are ____________ permeable only to _________________________-
phospholipid bilayers.
small nonpolar molecules
nuclear pore complexes are only channels for _____________,__________ and __________-
small polar molecules, ions, and macromolecules
______________________ : a fibrous mesh that provides structural support
consists of fibrous proteins (________) and other proteins
nuclear lamina
lamins
lamins are a class of intermediate filament proteins that associate to form higher order structures.
___________ interact to form a dimer: the alpha-helical regions wind around each other to form a coiled coil. the lamin dimers associate with each other to form the lamina
two lamins
mutations in lamin genes cause several inherited tissue-specific diseases. The bases of the pathologies in each of these disease is unclear _______________
hutchinson gliford progeria
lamins bind to inner __________ such as emerin and lamin B receptor (LBR)
the y are connected to the cytoskeleton by LINC protein complexes
lamins also bind to _________
inner MEMBRANE PROTEINS
TO CHROMATIN
_______________ are composed of about 30 different pore proteins (nucleoporins)
- RNAs synthesized in the nucleus must be exported to the cytoplasm for protein synthesis
- proteins needed for nuclear functions must be imported from synthesis sites in the cytoplasm
- molecules pass through pore complexes by two mechanisms
- __________________- small molecules pass freely in either direction
- __________________-are selectively transported ;requires energy
NUCLEAR PORE COMPLEXES= are composed of about 30 different pore proteins (nucleoporins)
PASSIVE DIFFUSION
PROTEINS AND RNA
electron microscopy shows pore complexes have _______ subunits organized around a large central channel
8 subunits
_________________ are connected to rings at the nuclear and cytoplasmic surfaces
the ____________ surrounds a ____________.
protein filaments extend from the rings, forming a basketlike structure on the nuclear side
the SPOKE RING ASSEMBLY surrounds a CENTRAL CHANNEL
proteins that must enter the nucleus have amino acid sequences called ________________-
these signals are recognized by _______________
nuclear localization signals were first identified in 1984, using a viral replication protein SV40T antien
the amino acid sequence is responsible for nuclear localization was determined using T antigen mutants.
when the same sequence was attached to other proteins, they were also transported to the nucleus
nuclear localization signals
nuclear transport
the ________ nuclear localization signal is a signal stretch of amino acids
others are ___________ consisting of two amino acids sequences separated by another amino acid sequences
T antigens
bipartite (nucleopasmin)
nuclear localization signals (NLS) are recognized by receptors called _____________, which carry proteins through the nuclear pore complex
importins work in conjuction with the GTP-binding protein __________, which controls directionality of movement
importins bind to the __________ of a protein, then to nuclear pore proteins and the complex is transported across the membrane
importins
ran
NLS of a protein
Ran/GTP binds to the importin, and this complex is transported by into tthe cytoplasm. Ran GAP hydrolyzes the GTP on Ran to GDP, releasing the importin. The Ran/GDP formed in the cytoplasm is then transported back to the nucleus by its own import receptor, where Ran/GTP is regenerated
General informaiton
protiens export from the nucleus:
proteins are targeted for export by amino acid sequences called _______________________-
NES are recognized by receptors in the nucleaus (_______), which direct protein transport to the cytoplasm
export signals (NES)
exportins
many importins and exportins are members of _______ known as _____________________
are members of A FMAILY OF NUCLEAR TRANSPORT RECEPTORS and KARYOPHERINS
General information:
exportins form stable complexes with cargo proteins in association with Ran/GTP in the nucleus
in the cytoplasm, GTP hydrolysis and release of Ran/GDP leads to dissociation of the cargo protein
general information
RNAs are transported to the cytoplasm as ribonucleoprotein complexes (RNPs)
karyopherin exportins transport ____________, _________, _____________
tRNAs, rRNAs, miRNAs
mRNA transport does not involve karyopherins and is independent of Ran.
a distinct transporter complex moves the mRNA through the nuclear pore
_________________, on the cytoplasm side releases the mRNA and ensures unidirectional transport
helicase
“transport of snRNAs between nucleus and cytoplasm”
- many small RNAs (snRNAs and snoRNAs) function within the nucleus.
- snRNAs are exported from the nucleus by an exportin (Crm1)
- in the cytoplasm, the snRNAs associate with proteins to form snRNPs, which are recognized by an importin and transported back to the nucleus
___________________________
small nuclear ribonucleoprotein particles (snRNPs)
regulation of protein transport is a mechanism for controlling protein activity _____________________
example: regulation of import and export of transcription factors is a way of controlling gene expression
in one mechanism, transcription factors or other proteins associate with cytoplasmic proteins that mask their NLS, and so they remain in the cytplasm
transcription facotr NF-kB is complexed with lkB in the cytplasm
if IkB is phophorylated and degraded by ubiquitin-mediated proteolysis, NF0kB can enter the nucleus and activate transcription of its target genes
in the nucleus
chromatin becomes highly _____________ during mitosis to form the compct metaphase chromosomes
during inter phase, most of the chromatin ____________ and its distributed throughout the nucleus
but even in interphase, the chromosome occupy distinct regions and are organized such that transcriptional activity of a gene is correlated with its position
DNA replication and transcription first takes place in clustered regions within the nucleus
highly condensed
decondenses
eahc chromosome was found to occupy a discrete region of the nucleus called the _______________
in _______ cell nuclei, each chromosome occupies a discrete region of the nucleus
recent studies have demonstrated that individual chromosomes also occupy distinct territories in mammalian cell nuclei
chromosome territory
drosophila cell
in situ hybridization with fluorescent probes specific for repeated sequences on individual chromosomes has been used to visualize the location of chromosomes within a nucleus
general information
