Non Coding RNAs and Disease Flashcards
2006
In 2006, Andrew Fie and Craig Mello won the Nobel prize for medicine for their work on “RNA interference- gene silencing by double stranded RNA”
RNA interference pathway is an Epigenetic method where gene silenced by small RNA’s binding to them, blocking their transcription or translation
-RNA now has function
ncRNAs are involved in disease
Pathogenesis: development and progression of disease
Therapeutics: treatment of disease
Biomarkers: diagnosis and prognosis of disease
-drug and protein serum tests
Central Dogma of molecular Biology
1958 Francis Crick, one of the discoverers of the DNA double helix structure, described that genetic info flows from DNA –> RNA –> protein in a simple linear manner
Specialised Mechanisms:
1. RNA –> DNA. Reverse Transcription. seen in virus
2. RNA –> RNA
mRNA encode proteins
Translation RNA’s= Non-coding RNA’s = rRNAs and tRNAs = ribosomal and transfer RNAs
RNA importance in the future
Total RNA
1) Coding RNA 1.5%–> mRNA
2) Noncoding RNA 98.5% (has regulatory roles)—>
a) Long ncRNAs (>200nt)
- Signal, Decoy, Guide, Scaffold IncRNA
b) Small ncRNAs (
Organism Complexity
Can judge the increasing organism complexity, by the amount of transcribing RNA that it makes
- same number of protein coding genes as other species
- huge amount of Non-coding RNA, that allows for complexity
e. g Bacteria vs Yeast vs Worms vs Humans
Non-coding RNA publications
Rapid increase in the number of publications due to increase in mRNA interest
What are Non-coding RNAs?
Classified into many subtypes within two major groups, defined by size (not function)
-200nt “long”ncRNAs
All forms have varied regulatory roles within the cell, some well characterised (tRNA), some not
Examples of Small ncRNAs
70-100 nt trasnfer RNAs (tRNA)
-carry a/acids for building growing peptide chain during translation
70-120 nt small nucleolar RNAs (snoRNA)
-involved in translation. modify ribosome. involved in direct splicing of mRNAs (can make different protein isoforms). associated with many different disease types
18-26 nt microRNAs (niRNA)
-distinctive hairpin structure
-work v similarily with siRNA (the F and M won nobel prize for)
tRNAs general
Identified in 1958
-well characterised non-coding RNA
-clover leaf structure
-bind to read mRNA, identify in triplets which a/acids should come to the growing peptide
Vital for correct translation of proteins
-error in tRNA = problems with protein production
tRNA in human disase
MELAS syndrome:
Mitochondrial myopathy, Encephalomyopathy, Lactic Acidosis and Stroke-like episodes
-Maternal Mitochondrial inheritance
-tRNA normally encoded on mitochondrial DNA that is 12 kilobases, inherited through mother
-this extra piece of DNA/mitcohondrial genome encodes quite alot of these tRNAs
-A3243G mutation tRNALeu ^UUR causes a/acid misincorporation
-A–>G switch
-effects mutiple organs
-errors in mitochondria genome tRNAs results in a single nucleotide mutation
How are tRNA’s mutated
tRNA are a gene
can be mutated in the same way as any other protein coding mRNA
snoRNA general
snoRNAs act as a guide for RNAs for modification of ribosomal RNA and tRNA’s
are crucial in ribosome biogenesis = translation of RNA into protein
-names in 1981
-discovered in late 60s
2x forms:
-C/D box, methylation (modify ribosomal RNA so they function properly) (if they dont function properly there will be translation problems)
-H/ACA box, pseudouridylation
snoRNA transcription
snoRNA sit within protein coding genes
- snoRNA host gene
1. Primary RNA transcription (including all exons and introns with their snoRNAs)
2. RNA processing (splicing of exons and removal of introns) –> - highlights that the “junk” discarded proteins actually contain regulatory RNAs
- ensures youre not wasting anything
a) Cytoplasm (mRNA used for protein)
b) Further processing–> snoRNAs - -> nucleolus
snoRNA and human disease
Prader-Willi and Angelman syndromes
-Loss of imprinted(methyl groups) region C15q11-13 (long arm), paternally expressed, included six snoRNAs (chromosome 15 long arm has methyl groups expressed only from father’s copy)
-SNORD116 mice show a defect in growth and feeding regulation (have different roles in different syndromes. losing more than one gene, and more than one function, changing the effect on more than one gene ==> get an effect on more than one organ)
-SNORD115 also causes alternative splicing of seratonin receptor 2C so loss of the sno causes different isoforms of 5-HC2cR –> growth retardation, increased energy expenditure
Illustrates how snoRNAs are directly associated with the development of disease
microRNAs
• Initially identified in C. elegans in 1993 and found conserved in animals in 2000
Mutations (knocked out) in the C. elegans let-7 (lethal) miRNA gene result in developmental abnormalities that often lead to rupturing of the worms (leak out of insides/burst of vulvo) and lethality
• First associated with human disease in 2002, miR-15/-16 deleted in chronic lymphocytic leukemia (Calin GA et al PNAS 2002, 99(24):15524-9) (pair of microRNA in region, and their loss was directly associated wiht the development of the leukemia)
• So well studied now – online database (inks different microRNAs with different disease states)
• In miRBase V21 (June 2014) contains 2588 miRNAs