91335 Lecture 3: Lecture 3- Diverse Roles Of RNA
MB2 Lecture 3
9/4/18
The diverse roles of RNA
RNA
Single stranded- more structure, flexible
RNA world theory
RNA first molecule to exist
Not very stable
Can self-assemble to form polymer function as enzyme (ribozyme)
Genetic complexity
Increase in complexity has to do with the amount of RNA
Research
Mutations can alter processing or final function of RNA/proteins
Can result in disease
mRNA
only class that is translated and coding
Single RNA strand of varying length
Specific DNA sequences delineate where transcription begins and ends
Mature mRNA
CDS = Coding Sequence, translated to form a polypeptide
Start odo is alas AUG hih odes for ethioie M aio aid
Stop odo sigals teriatio of traslatio ad does NOT ode for a aino acid
UAG, UAA or UGA
5` UTR (leader) sequence
– Recognised by ribosome allowing for translation
initiation
3` UTR (trailer) sequence
– Contains sequences which regulate translation
– Required for translation termination and post- transcriptional modifications
RNA splicing
Spliceosome cuts the mRNA to release introns and join flanking exons
Code for one polypeptide is NOT continuous in DNA
Spliceosome is a collection of small nuclear ribonucleoproteins (snRNPs) which recognise
sequences within the intron that signal splicing
snRNPs composed of protein and small nuclear RNA (snRNA)
where to splice
5 ed: GU
3 ed: AG
branch point sequence (BPS): Conserved Adenosine required for initial splicing step
find more resources at oneclass.com
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small nuclear RNA (snRNAs)
bind to complementary sequence of pre-mRNA substrate
guiding function to bring spliceosomes to correct site
also, catalytic role in spliceosome
alternative splicing
single gene coding for more than one polypeptide via different combinations
98% of human genes are alternatively spliced
increase protein diversity
Importance
Can be tissue specific
Mutations and mismatching
Summary
Processing hnRNA to mature mRNA is dynamic
mRNA sequence changes dramatically from genomic sequence
mRNA is subject to many regulatory pathways controlling its expression, stability and
function
Translation
Types of RNA molecules involved
– Mature mRNA
• Contains sequence to be translated
– Ribosomal RNA (rRNA)
• Component of the ribosome, the translational machinery
– Transfer RNA (tRNA)
• Transfers amino acids to ribosome in codon- dependent manner
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Can self-assemble to form polymer function as enzyme (ribozyme) Increase in complexity has to do with the amount of rna. Mutations can alter processing or final function of rna/proteins. Can result in disease mrna only class that is translated and coding. Specific dna sequences delineate where transcription begins and ends. Cds = coding sequence, translated to form a polypeptide (cid:858)start(cid:859) (cid:272)odo(cid:374) is al(cid:449)a(cid:455)s aug (cid:449)hi(cid:272)h (cid:272)odes for (cid:373)ethio(cid:374)i(cid:374)e (cid:894)m(cid:895) a(cid:373)i(cid:374)o a(cid:272)id (cid:858)stop(cid:859) (cid:272)odo(cid:374) sig(cid:374)als ter(cid:373)i(cid:374)atio(cid:374) of tra(cid:374)slatio(cid:374) a(cid:374)d does not (cid:272)ode for a(cid:374) a(cid:373)ino acid. Recognised by ribosome allowing for translation initiation. Required for translation termination and post- transcriptional modifications. Spliceosome cuts the mrna to release introns and join flanking exons. Code for one polypeptide is not continuous in dna. Spliceosome is a collection of small nuclear ribonucleoproteins (snrnps) which recognise sequences within the intron that signal splicing snrnps composed of protein and small nuclear rna (snrna) where to splice. 98% of human genes are alternatively spliced increase protein diversity.
