Cell Nucleus Flashcards
What are the three major components of the nucleus
Nuclear Envelope, Nucleolus, and chromatin
Describe nuclear envelope
two membrane system (inner an outer, differ in structure and fxn) perforated by nuclear pores that separates the nucleoplasm from the cytoplasm
What processes are taken place in the nucleolus?
site of rRNA synthesis and regulation of the cell cycle
Contents of chromatin
nuclear material containing DNA and various nuclear proteins
What is the nucleoplasm
nuclear content (not chromatin) and nucleolus
What separates the inner and outer membrane of the nuclear envelope?
the perinuclear cisternal space, which is continuous with the cisternal space of RER
Describe Outer nuclear membrane
continuous with rER and contains ribosomal docking proteins for polyribosomes
Describe Inner nuclear membrane
supported by nuclear lamina and contains lamin receptors and lamin-associated proteins that secure its attachment to nuclear lamina
What is the nuclear lamina?
rigid network that of intermediate protein filaments that supports inner membrane of nuclear envelope…scaffolding of chromatin, membrane of nucelar envelope and spacing of nuclear pore complex… essential for DNA replication and transcription
What is the nuclear lamina composed of?
mainly lamin A/C proteins, attached to inner membrane through lamin B protein
What do lamin A/C proteins form?
form intermediate filaments that are crossed linked into an orthganal lattice
How does lamin B attach lamin A/C proteins to membrane?
through interactions with lamin receptors in inner membrane
What are the lamin receptors in inner membrane and what do they bind?
nurim (binds lamin A), emerin (binds lamin A and B), and lamin B receptor (binds lamin B)
What are laminopathies and what regions of the body are affacted?
tissue specific diseases that affect striated muscle, nerve or skeletal development and premature aging caused by mutations in lamin and their receptors
EDMD (muscular dystrophy)
laminopathy characterized by muscle weakness and wasting in the upper and lower limbs and cardiomyopathy
X-linked EDMD
caused by mutations in emerin
AD EDMD
caused by mutations in lamin A/C proteins
How is the nuclear envelope formed?
from the merging of the inner and outer cell membrane
NPC composition
eight multidomain protein subunits arranged in a central framework insterted between a cytoplasmic ring and a nucleoplasmic ring, attached to a terminal ring.
Cryoelectron Tomography CET
version of electronmicroscopy where 3D images are crated from 2D ones
How does the central pore of the NPC behave?
as a gated channel or bidirectional communication gate
How are large particles imported to nucleus?
Contain NLS (nuclear localization AA seq) that binds to importin receptors in a GTP-dependent fashion controlled by RAN signalling
ow are large particles exported from nucleus?
proteins with NES seq bind to exportin and to RAN-GTP molecule
Nucleosomes
smallest unit of chromatin and first level of folding… dna coiling (2 loops) around protein core of 8 histones (h1-h4)
