Sub-nuclear Structures Flashcards
What are the three major components of the nucleolus?
Fibrillar centres (FC), dense fibrillar components (DFC) and granular components (GC).
What is the nucleolus composed off?
Proteins and Nucleic acids
What are the three types of nuclear proteins?
Those mostly in the nucleolus: fibrillarin and nucleolin.
Those partially in the nucleolus: ribosomal proteins.
Time/condition dependent: p68 and cell cycle factors.
What is the pivotal role of the nucleolus?
Ribosome biogenesis.
What are ribosomopathies?
A collection of disorders I’m which abnormalities cause impaired ribosome biogenesis.
Give the three ribosomopathies?
Diamond-Blackman Anemia, treacher Collins syndrome, dyskeratosis congenital.
What is the mutation in diamond-blackman Anemia?
Mutation in ribosomal protein S19.
What are the symptoms of diamond-Blackman anaemia?
Low red blood cell count lead to a variety of congenital abnormalities. Craniofacial malformations, upper limb abnormalities, cardiac defects.
What is the mutation in treacher Collins syndrome?
TCOF1 gene mutation, which encodes a nucleolar protein treacle.
What are the craniofacial deformities in treacher Collins syndrome?
Absent cheekbones, a small lower jaw and malformed or absent ears.
What is the mutation in dyskeratosis congenital?
Mutation in DKC1, which encodes dyskerin.
What are the symptoms of dyskeratosis congenital?
Progeria.
What are many nucleolus associated diseases associated with?
Changes in ribosome biogenesis and sequestration or loss of proteins.
What are the two links between ribosomes and cancer?
Increased ribosome biogenesis (satisfies deman in proliferation, evidence of proto-oncogenes can up regulate ribosome biogenesis) and deficiencies in ribosome function.
What is c-Myc?
A proto-oncogene which is up-regulated in a variety of leukaemia’s and solid tumours.
What does the up-regulation of c-Myc lead to?
Increased rRNA transcription and ribosome biogenesis.
Why do viruses target the nucleolus?
To redistribute cellular proteins into or out of the nucleolus.
Give two examples of virus’ associated with the nucleolus?
Coronaviruses and KSHV
What do splicesomes consist of?
U1, U2, U4, U5 and U6 small nuclear RNPs with a large number of proteins in a highly dynamic and complex structure.
What are Cajal bodies involved in?
The maturation and assembly of splicesomal sub complexes particularly snRNPs.
What are the sub nucleur structures similar to Cajal bodies?
Gems
What is the difference between gems and Cajal bodies?
Gems do not contain snRNPs but do contain SMN which functions in snRNPs biogenesis.
What are nuclear speckles?
Structures enriched in pre-mRNA splicing factors located in the inter chromatin regions in the nucleoplasm for storage modifications and for pre-mRNA splicing factors.
Where are nuclear speckles always situated?
Close to active genes
What are polycomb bodies?
Hubs for gene repression and usually associated with heterochromatin.
What are PML nuclear bodies?
Functionally promiscuous sub nuclear structure which regulate several diverse cellular function.
What is the mutation in spinal muscular atrophy?
A genetic mutation in the SMN1 gene which encodes SMN a major Cajal body and gem protein.
What are the symptoms of spinal muscular atrophy?
Death of neuronal cells in the anterior horn of the cord in subsequent system-wide muscle wasting (atrophy)
What is retinitis pigmentosa?
A genetic eye condition in which the vision progresses from night blindness to runner vision to complete blindness caused by the progressive loss of the rods and cones in the retinal pigment epithelium.
What is the mutation that causes retinitis pigmentosa?
Genetically linked to mutations in splicing factor PRP31
What is acute promyelocytic leukaemia caused by?
Mutations in PML proteins.
