Nuclear Periphery and Nucleocytoplasmic transport Flashcards
what are 3 features in the structure of nuclear envelope
double membrane
nuclear pore complex
nuclear envelope
two points about nuclear pore complex
tight control
differs on each side of membrane
describe a double membrane
two lipid bilayers
what is the nuclear pore complex made up of
subunits- on average 8
what supports the nuclear envelope
nuclear lamina
why does the nuclear envelope need support
to strengthen
communication
etc
where is the lamina located
beneath the inner nuclear membrane
what filaments are present in lamina
intermediate filaments similar to cytoplasmic filaments
how is the lamina anchored to nuclear envelope
membrane protein anchorage
lipid modifications of proteins on lamina to anchor
direct interactions between NPC and lamina
what are the mutationsin lamina associated with
hutchinson-gilford progeria syndrome(inherited premature ageing condition)
how do HGPS cells differ from healthy cells
wrinkled structure
how do molecules get from nucleus to cytoplasm
nuclear pore complex
whar are karyopherins
importins and exportins
move molecules in and out
what are RanGTP/RanGDP
ras-related nuclear protein bound either to GTP or GDP
what is the function of RanGTP/RanGDP
controls the direction of nuclear transport via a carefully maintained gradient across nuclear envelope
what is RanGAP
ran GTP-ase activating protein- cytoplasmic
what is RanGEF
ran guanine nucleotide exchange factor (attached to chromatin)
what is the protein export cycle
moves cargo out of nucleus
must bind as trio of molecules
cargo RAM GTP can bind to export complex
goes into cytoplasm
RAMGAP enzymes spot RAMGTP in cytoplasm and remove phosphate so that RAMGTP no longer binds
complex falls apart and so RAMGDP can pass through pore on its own
what is the protein import cycle
binding to importin can bind complimentary no additional factor
RAMGTP recognises importing and binds it
comformational chnage and so cargo can no longer bind
RAMGTP into cytoplasm, phosphate removed
what is the cargo associated with facillitated diffusion model
importing
how is karyopherin involved in facillitated diffusions
protein has binding site for FxFG repeats - FG repeats on nuclear pore proteins
how is facciliateted diffusion helped
via binding with FG repeats
where do rna exist
as ribonucleoprotein complexes
describe the transport of RNAs
tTRNA out
hnRNA out
u-snRNA out
what is U-snRNA
involved in protein assembly in cytoplasm- protein complex then imported back into nucleus
what is a TAP complex
induces splice junction
why are splice junctions important
when exporting
allow them to act as export proteins for RNA
what happens to RNA as it diffuses out of pore
forms transient interactions with NPC and this twists RNA
RNA more likely to move in same direction
what are Dbp5 twists
in RNA to make move in same direction
