VOLK Flashcards
The nucleus is encased by two-unit membranes forming the _________.
nuclear envelope
The _____ nuclear membrane is continuous with the endoplasmic reticulum (ER) system.
outer
The outer nuclear membrane is studded with ________.
ribosomes, giving it a “rough” appearance
The inner nuclear membrane associates with _______.
heterochromatin
________ represent discontinuities in the nuclear envelope structure through which physical communication can occur.
Nuclear pores (NP)
Immediately underlying the nuclear envelope is a filamentous mesh-work called the nuclear ______.
lamina
The nuclear lamina is composed primarily of proteins called ______.
lamins
There are _____ major types of lamins.
3
Lamins are members of the family of ______ filament proteins.
intermediate
The nuclear lamina is assembled into a _____-dimensional sheet-like lattice.
two
Nuclear pores have ________ symmetry.
octagonal
There are approximately ________ nuclear pores per cell.
3000-4000
Nuclear pores are ______-shaped.
donut
Gene _______ is regulated by the Nuclear Pore Complex (NPC).
transcription
________ chromatin associates with interior transcription factories.
Active
_______ chromatin is peripherally located at the nuclear envelope.
Inactive
The ________ is a subnuclear body.
nucleolus
The nucleolus is _____ membrane bound.
not (!!)
The nucleolus is visible by both ______ and _______ microscopy.
light, electron
The nucleolus is the site of ________ gene clustering
rDNA
The nucleolus is the site of ______ synthesis, and _________ assembly.
rRNA, ribosome
__________ factories are distinct regions within the nucleus that have transcription occurring.
Transcription
If one nucleus is analogous to Lake _______, then a protein is analogous to a ______ in terms of scale within the nucleus.
Lake Ontario, person
The speed of molecules moving within the nucleus would need to be analogous to ________.
9000 mph
Membrane-less _______ are formed by phase separation.
compartments
The Nuclear Pore Complex (NPC) is involved in the passage of nuclear and _______ molecules.
cytosolic
_______ molecules can freely diffuse through nuclear pores.
Small
Small molecules that can freely diffuse through nuclear pores are typically proteins less than ______ kDa.
50
_________ transport is required for larger molecules to pass through nuclear pores.
Active
Larger molecules interact with _________ to undergo active transport through nuclear pores.
FG nucleoporins
The Nuclear Pore Complex is up to ______ MDa in size.
125
The Nuclear Pore Complex is composed of _______ proteins.
500-1000
There are approximately ______ different types of nucleoporins.
30
Most proteins are synthesized in the ________.
cytoplasm
Proteins functioning in the nucleus control of _________.
DNA replication
Proteins functioning in the nucleus regulate _________.
transcription
The _______ dictates nuclear import.
Nuclear Localization Sequence (NLS)
An NLS is a stretch of ________.
amino acids
A common NLS sequence is -Lys-Lys-Lys-Arg-Lys-, which is rich in ________ amino acids.
positive
NLS sequences are ________ for nuclear import.
necessary
Mutating an NLS will prevent a protein from entering the ________.
nucleus
The NLS is ______ to localize proteins into the nucleus.
sufficient
Normally cytoplasmic proteins tagged with an NLS become ________.
nuclear
Many proteins need to be actively ________ from the nucleus.
exported
All ________ is synthesized in the nucleus but mostly functions in the cytosol.
RNA (mRNA, rRNA, tRNA)
RNA molecules generally need to be “______” in the nucleus prior to export.
processed
A leucine-rich sequence called the _________ facilitates nuclear export.
Nuclear Export Sequence (NES)
The consensus NES is _________.
Leu-X1-2-Leu-X2-3-Leu-X-Leu
Diffusible small proteins need to be actively ________ from the nucleus.
excluded
_________ factors that function in gene expression by regulated import/export need to be shuttled out of the nucleus.
Transcription
Assembled ________ (a form of RNP) need to be shuttled out of the nucleus.
ribosomal subunits
Large _______-containing proteins that may function in both the nucleus and cytoplasm need to be shuttled out of the nucleus.
NLS
Proteins that are actively exported contain both an _______ and an ________.
NLS, NES
_________ are chaperones that bind to the NLS for nuclear import.
Importins
_________ are chaperones that bind to the NES for nuclear export.
Exportins
______ is a key regulator of nuclear import and export.
Ran
Ran is a _____ protein.
G
The _______ form of Ran is associated with export.
GTP
The ______ form of Ran is associated with import.
GDP
_________ are found in the cytoplasm.
Ran-GAPs
______ are chromatin-bound.
Ran-GEFs
________ export is typically a Ran-independent process.
mRNP
mRNP stands for _______-containing complexes.
mRNA
mRNP (mRNA-containing complexes) export is typically a Ran-___________ process.
indepedent
GTP to GDP hydrolysis provides directionality for nuclear transport by creating _____________ of various protein complexes across the membrane.
concentration imbalances
Importin and exportin are recycled back through the pore by virtue of the same kind of ___________ that result in cargo transport.
concentration imbalances
