esone1
introne1
GT
S
P
L
I
C
I
N
G
esone2
AG
introne2
GT
esone3
AG
eliminazione introni
introne1
introne2
esone2
esone1
esone3
unione esoni
esone1
esone2
esone3
Alcuni modo di fare alternative splicing
Riconoscimento degli introni
Motivi conservati
Meccanismo
dello splicing
Particelle dello splicing
- SnRNPs (Small nuclear ribonuclear proteins) binds critical sites
on the pre-mRNA
- pronounced ‘SNURPs’
- these are complexes containing both protein and small RNAs
- the small RNAs are transcribed by RNA polymerase III
- they then associate with accessory proteins
- the complex then recognizes critical sites for splicing by base
pairing
Particelle che intervengono nello splicing
U1 snRNP
Intron definition exon definition
Modello di exonic splicing enhancer mediato da proteine SR
Modello di exonic splicing silencer
Modelli di splicing silencing
Nell’esone si trovano motivi ESE e ESS sovrapposti, quindi c’è una
competizione diretta tra i fattori che stimolano lo splicing (SR) e quelli che lo
inibiscono (hnRNP). Il legame di uno o dell’altro elemento è mutuamente
esclusivo.
A questo punto i fattori importanti diventano la maggiore affinità di legame degli
elementi regolativi e la concentrazione di questi.
Modelli di splicing silencing
Fattore inibitori per lo splicing si legano a elementi Intronic Splicing Silencer e
per dimerizzazione formano un anello che esclude l’esone
Modelli di splicing silencing
Se non ci sono elementi inibitori l’esone viene incluso, se ci sono elementi
inibitori e se questi si legano per primi, promuovono il legame di altri elementi
inibitori (polimerizzazione) od ostacolano il legame di elementi rafforzativi
Nonsense
mediated
decay
Why Splicing?
1. The intron-exon arrangement may facilitate the evolution of new proteins through
recombination of exons.
2. Splicing increases the coding potential of the genome through alternative splicing.
60% of transcripts in human are spliced in different ways.
Cell-type spcific splicing of fibronectin pre-mRNA
attggaaaccgaaacccgttggtcacctctgcaatagccctccctccctcacttctacaattttgtgaca
gtggtcttgttttctgcattctctgcttcacgtgcttgttttgttggagcgcgtttgcatgctgctttaa
attctgaaatattaaaaaaatttcgaagtttttcagcacatgggatgggagttttgaatttcaatttttt
aaaaacatttttctgtgattagtgccgtcgtggcacggctgttagccgcctatccggtttattcgatact
ttGTGAGTTTTTTGTAACTTTATGGTCGTCGAAATGGGAAAACTTGGCCACCAATATAAGTTTGGAAAAC
AATTTCCTAAAAATAAAATAATTGAACTTTTCCGATGAATAAAAAAATCGATCAGATATTCTGGAAAAAA
AATCGATAAATTAATCGATTTTCTTGGAAAATACATCGAAAAATTGAGAAAAATAGAAAAATGAATGTTT
TTCGATTACCGATTTATTGATTTTTCGTGAAAACTGAGTTCAGATAATTTTAAAAGCAATGTTTTTCATT
TTTCAAATCAGAATCACTATAGTTTTGAAAAATCAATAATTAATTTATTGATTTTTCAATATAATTTTTT
GGAAAAAATAGAAAAATCCCTTTCTAAAAGTTTTAAATTTCCAAGAAAAATTCATTTTCAAAATCACCAA
CGCGCTCTATAGAGTAGTCGATGAAAATCTCCGTTAAGGGTGCATGGGCAAAACGCGCTCGAACGACAAT
TGTTATTGTATGTTTGGTCTTGCAACGAAAAGTTTGAAAAATTGAAAAAAAGTTGTGTCTGATACATTTT
TTTTTGGCATTTTCTGCTATTTTACACCAGAAAAAATTTAATAAACATAAAAAATCGAAATTTTTCAAGT
TGGACAATTTTCAGtgagcatcttatccatcctagttctcagttcaggacttgtgcacattcgtttagag
ccagatattcgcaaagccttttcaccggatgattcagatgctggataGTAAGTGACTACTGACCTTGAAG
CCTCCTTCCTCCACCAGTCAGAAATAACACGTTTTTTCGCAATGTTTTTCTTTTTCTAATTCGATTTCCC
TTTCTCCCTTTCTTATTGTGATTTGGTCAATGTTTGGTTGACTGGGAAGAAAATTGAATTTTTTTGGAAT
TCCACTTGAAGTTAAAAAACCCAAAATAAATATTTGATCAAAAATAAATAAGAAAAAAAAGAAAACTTTA
AAGCAAATGAAAATTTCGTTCGTAACTATTTTGTTAATTTTTTTAAAACTCCTATTTTAAATATATGCTT
TTTGCGGAAATTTCTATAAATTTTTTTACATTTTTCAGtgaaacccgtgtctggctggaatactacggac
tcgacatctatccggaacgagcattctgtatttttaccgccaagcgcgaaaattccagtattctccagga
aggcgcactggcagacGTAAGTTGATTCTCCGTCACGCCCACTTTTCTGGCGGGAATTTAAAAAATTTCA
Gatttatactgtggacaatcgactatcggcggcagttggctaccaagatggggatggacgaaaaaattgc
gatccactctgcgacttgaacagcccctttcacttgttagcgGTAGGTGGTGGTCTAGGGTGTCATTTTT
CGATTTTTTCAATTATTCGATGTTTTTAGTGAAAATCGAAAAATCTAAAAATTGAAAATCGAAAAATGAA
AGAAACATTGTTTTTTGGGGACCAAACATCTTAATGAATTTAACAACAGGGAAAACTGAACAGAAACCTG
GACGGTCTTATCCCATTTATCTATATTCTTAAAATGAATGATGGAGAAAAAAGTTAAAATAAAAACATTA
TCAGCTTTTTGTAAGTTTTTCTCAAAAATTGTTCGATTTTTCGATTTTCTAAAAAGTCGAAAAACCGAAA
CCCTTGGTGGTGGTGGTGGTGGACTAGAAAACTCTTCAACGACCACATGGCAATTTTCAGaatttgacgc
ggagaaacaatggtaccacaagtgtattcacctatccggatatgccatatagcggactggatattttcct
gggacttcacttgagtaatgcggattttggtaagattttttttgaaatgttaaatgaaaagttgaaaaat
agtttttatgatttagccactttccagttaaaatttcatttttttaactataaaaagttctggaaaaatg
aatttctAGgccgccgatcctaaaAGTgcaccatttcgcAGaAGTacGTacAGTttcccatctatccctA
GTgGTcttGTtttctgcattctctgcttcacGTgcttGTtttGTtggAGcgcGTttgcatgctgctttaa
attctgaaatattaaaaaaatttcgaAGTttttcAGcacatgggatgggAGTtttgaatttcaatttttt
aaaaacatttttctGTgattAGTgccGTcGTggcacggctGTtAGccgcctatccgGTttattcgatact
ttGTGAGTTTTTTGTAACTTTATGGTCGTCGAAATGGGAAAACTTGGCCACCAATATAAGTTTGGAAAAC
AATTTCCTAAAAATAAAATAATTGAACTTTTCCGATGAATAAAAAAATCGATCAGATATTCTGGAAAAAA
AATCGATAAATTAATCGATTTTCTTGGAAAATACATCGAAAAATTGAGAAAAATAGAAAAATGAATGTTT
TTCGATTACCGATTTATTGATTTTTCGTGAAAACTGAGTTCAGATAATTTTAAAAGCAATGTTTTTCATT
TTTCAAATCAGAATCACTATAGTTTTGAAAAATCAATAATTAATTTATTGATTTTTCAATATAATTTTTT
GGAAAAAATAGAAAAATCCCTTTCTAAAAGTTTTAAATTTCCAAGAAAAATTCATTTTCAAAATCACCAA
CGCGCTCTATAGAGTAGTCGATGAAAATCTCCGTTAAGGGTGCATGGGCAAAACGCGCTCGAACGACAAT
TGTTATTGTATGTTTGGTCTTGCAACGAAAAGTTTGAAAAATTGAAAAAAAGTTGTGTCTGATACATTTT
TTTTTGGCATTTTCTGCTATTTTACACCAGAAAAAATTTAATAAACATAAAAAATCGAAATTTTTCAAGT
TGGACAATTTTCAGtgAGcatcttatccatcctAGTtctcAGTtcAGgacttGTgcacattcGTttAGAG
ccAGatattcgcaaAGccttttcaccggatgattcAGatgctggatAGTAAGTGACTACTGACCTTGAAG
CCTCCTTCCTCCACCAGTCAGAAATAACACGTTTTTTCGCAATGTTTTTCTTTTTCTAATTCGATTTCCC
TTTCTCCCTTTCTTATTGTGATTTGGTCAATGTTTGGTTGACTGGGAAGAAAATTGAATTTTTTTGGAAT
TCCACTTGAAGTTAAAAAACCCAAAATAAATATTTGATCAAAAATAAATAAGAAAAAAAAGAAAACTTTA
AAGCAAATGAAAATTTCGTTCGTAACTATTTTGTTAATTTTTTTAAAACTCCTATTTTAAATATATGCTT
TTTGCGGAAATTTCTATAAATTTTTTTACATTTTTCAGTgaaacccGTGTctggctggaatactacggac
tcgacatctatccggaacgAGcattctGTatttttaccgccaAGcgcgaaaattccAGTattctccAGga
AGgcgcactggcAGacGTAAGTTGATTCTCCGTCACGCCCACTTTTCTGGCGGGAATTTAAAAAATTTCA
GatttatactGTggacaatcgactatcggcggcAGTtggctaccaAGatggggatggacgaaaaaattgc
gatccactctgcgacttgaacAGcccctttcacttGTtAGcgGTAGGTGGTGGTCTAGGGTGTCATTTTT
CGATTTTTTCAATTATTCGATGTTTTTAGTGAAAATCGAAAAATCTAAAAATTGAAAATCGAAAAATGAA
AGAAACATTGTTTTTTGGGGACCAAACATCTTAATGAATTTAACAACAGGGAAAACTGAACAGAAACCTG
GACGGTCTTATCCCATTTATCTATATTCTTAAAATGAATGATGGAGAAAAAAGTTAAAATAAAAACATTA
TCAGCTTTTTGTAAGTTTTTCTCAAAAATTGTTCGATTTTTCGATTTTCTAAAAAGTCGAAAAACCGAAA
CCCTTGGTGGTGGTGGTGGTGGACTAGAAAACTCTTCAACGACCACATGGCAATTTTCAGaatttgacgc
ggAGaaacaatgGTaccacaAGTGTattcacctatccggatatgccatatAGcggactggatattttcct
gggacttcacttgAGTaatgcggattttgGTaAGattttttttgaaatGTtaaatgaaaAGTtgaaaaat
AGTttttatgatttAGccactttccAGTtaaaatttcatttttttaactataaaaAGTtctggaaaaatG
Distribuzione dimensioni introni C.elegans
0,09
0,08
0,07
frequenze
0,06
0,05
0,04
0,03
0,02
0,01
0,00
2222 3334 4455 5566 6777 8888 999 1111 1111 1111 1111 1111 1111
0369 2581 4703 6925 8147 0369 258 0001 1112 2233 3444 4555 6667
1470 3692 5814 7036 9258 1470
dimensioni
basi
gtttttt
gtttctg
gttcgtt
gttgttc
gtgagaa
gttgcta
gtgtgtt
gttctgt
gtgggtt
gttccgg
gttatgc
gttacga
gtgttct
gtgcgtt
gtgtccg
gtggtcc
gtggcca
gtcagtt
gtgctat
gtgccag
gtgatac
0,10
gtgacaa
gtaggtt
gtctgtt
gtctatg
gtcggtc
gtcgata
gtccggt
gtccagg
gtatttt
gtcaggc
gtcaaga
gtacgtt
gtatgct
gtatacg
gtaattt
gtaggcc
gtagaca
gtacgat
gtacaag
0,02
gtaagac
gtaaaaa
frequenze
Sequenze in testa negli introni di C.elegans
gtaagtt
gtgagtt
0,08
0,06
0,04
gttagtt
gtatgtt
gtttgtt
gttggtt
0,00
basi
ttgaaag
ttaaaag
agttcag
tggaaag
tattcag
tgaaaag
tcgaaag
tcaaaag
aattcag
tagaaag
taaaaag
ctttcag
gtgaaag
gtaaaag
gggaaag
ggaaaag
gcgaaag
gcaaaag
gagaaag
gaaaaag
0,05
ctgaaag
ctaaaag
cggaaag
cgaaaag
ccgaaag
ccaaaag
cagaaag
caaaaag
atgaaag
ataaaag
acttcag
aggaaag
agaaaag
acgaaag
acaaaag
aagaaag
aaaaaag
frequenze
Sequenze in coda negli introni di C.elegans
0,25
ttttcag
0,20
0,15
atttcag
0,10
tttccag
gtttcag
tcttcag
0,00
Terne che precedono gli introni in C.elegans
0,14
0,12
0,08
0,06
0,04
0,02
basi
ttt
att
cgt
gct
tat
aat
ctg
ggg
tcg
acg
cag
gtc
tgc
agc
ccc
gac
tta
ata
cga
gca
taa
0,00
aaa
frequenze
0,10