BCH3031 Lecture Notes - Lecture 13: Noncoding Dna, H3K4Me3, Epistasis
Lecture 13 – The Emerging Role of Long NonCoding RNAs in Cells
Versatility of RNA
• Junk DNA
o Number of genes is not correlated to genome size or with organismal
complexity
o Vertebrate genomes can produce more than one polypeptide per gene
because of alternative splicing of RNA transcripts
o Controversial: if its not coding it must be junk
Diversity of RNA functions
• Can encode information
• Or be substrate for producing proteins
• Binds on base pairing – efficient at finding its targets
• Can form 3D structures (RNA aptamers) – interact with specific substrates
• Can be direct – non coding RNAs allows it to produce a transcript – can be
functional straight away after decapping or degraded
• Flexible in mismatching base pairing
o Provide flexibility in system – mutant RNA retains ability to recognise
its target
• Complexity of interactions: 4 nucleic acid and protein interactions
o RNA-protein
▪ Gene regulated by RNA and protein
▪ RNA binding on specific sequences on genome → transcription
factors (activator or suppressor)
o DNA-RNA
o Protein-DNA
o RNA-RNA
Characteristics of long non-coding RNAs
• E.g. lncRNAs
o Mostly RNA polymerase II (RNA Pol II)
o Can sequence it
o Promoter can identify
▪ H3K4me3 (promoter): Histone 3, lysine 4 and trimethylated
▪ H3K36me3 (gene body): histone 3, lysine 36, trimethylated –
region of gene that is going to be transcribed
o >200 nt long
o May undergo splicing or comprise of single exon
o Most are processed just like mRNAs (cap and polyA tail)
o Dynamic and diverse in function
How long non-coding RNAs were identified
• Identifications of lncRNAs
o Tiling arrays
▪ cDNA is hybridized to microarray slides
o SAGE
▪ Short stretches of unbiased cDNA sequence (SAGE tags) by
restriction digests
o CAGE
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