Nucleus, Signal, Death, Division Flashcards
(53 cards)
Chromatin
DNA is found wrapped around Histones
Euchromatin is lighter, allows expression
Heterochromatin- present in the structural centromere, nuclear lamina and telomeres.
Facultative heterochromatin can switch between states
RNA splicing islands
Nucleolus has chromatin organised into islands of DNA and RNA
Chromosome territory
The DNA from each chromosome occupies a distinct territory.
Short parts can be de condensed, transported to transcription islands and recondensed
Nucleolus
Site of ribosome production, which are essential for translation
Speckles
Sites of accumulation of splicing factors, but not splicing itself.
Used as storage.
Cajal body
Formation of essential splicing factors
Contains:
Coilin
SMN (survival of motor neurons protein)
Role in biogenesis or snRNP splicing factors
SMN mutations -> spinal muscular dystrophy
Ribosome creation
Genes from different chromosomes are brought together and transcribed creating large amount of RNA
Nucleoplasmic transport
Nuclear proteins bind to nuclear import receptors allowing them to travel through the pore
Transcription factors are created and then imported into the nucleus for gene regulation
Bidirectional, energy requiring and regulated
Things travelling into the nucleus
Matrix proteins Lamins Chromatin components Enzymes Transcription factors Conditionally cytoplasmic proteins
Things travelling out of the nucleus
Mature mRNA
tRNA
rRNA as subunits
SRPs
Inside of the nuclear lamina
Alpha helices wrap around to form a coiled coil
Lamina CNS be phosphorylated by normally associated head to head
Tetramer then form criss cross patterns
B type lamins
Near the nuclear membrane and bind to integral proteins inside that membrane
Are then isoprenylated (lamin B receptor)
A/C lamins
Inside next to the nucleoplasm, phospharylated.
Functional organisation of the nucleus
Phosphorylation triggers disassembly of the lamina and nuclear envelope
-> vesicles
Dephosphorylation reforms the nuclear (mitosis etc.)
Functions and structure of the nucleus
DNA transcription
RNA modification
Ribosome assembly
DNA replication and repair
Kept centrosomes in the cell by micro tubules
Surrounded by 2 bilayers with a lumen that is continuous with the ER
Cadherins
E cadherin - epithelial (ectoderm)
N cadherin- neural
Calcium allows stretching out and interaction
Most homophilically some heterophilically
NCAM and ICAM
Immunoglobulins
Mediate Ca+ independent cell- cell adhesion
Selectins
Expressed on surface on WBCs
Helps slow down
Uses integrin to pass through endothelium
Adherens junctions
Actin filaments bind to alpha-catenin
Catenins link to cadherins
When myosin pulls on actin, forms dip in membrane
Can be used for endocytosis
Tight junctions
Seal between cells
Barrier between plasma domains
NA+ glucose transporters allow glucose into cell
At the basal lamin da straight diffusion is allowed
Separate transporter proteins into groups
Claudin and occlusion sew cells together, 4 pass membrane
Desmosomes
Give epithelia mechanical strength
Connects intermediate filaments in neighbouring cells
Intermediate filament -> desmoplakin -> plakoglobin + plakophilin -> desmoglein + desmocollin
Hemidesmosomes
Bind the basal lamina (bottom of cell)
Anchors intermediate filaments to extra cellular matrix
Gap junctions
Couple cells electrically and metabolically
Connexins -> 2 stacked hexamers (connexons)
Homotypic or heterotypic
Extra cellular matrix
Proteoglycans- GAG chains covalently linked to core protein
Core protein linked by serine -> tetrasaccharide -> GAG
Fibrous protein (collagen)
Glycoproteins
Hyalauron with sulphate glycoproteins fills large volumes. Binds cations and water and regulated movement
Can affect stability and activity of proteins
Organisation of collagen
Cells organise collagen by exerting tension
Fills environment
Type 9 can modify type 2