Page 256 - Color Atlas of Biochemistry

RNA maturation 247

A. 5' and 3' modification B. Splicing of hnRNA: mechanism
of mRNA
5' splicing Branching 3' splicing
O
CH 3 site point site
C N
HN C 7
C H O O a) 5' ...AGGU... ...GAC... ...CAGG... 3'
C C 5'
H 2 N N N H 2 C O P O P O 5' exon Intron 3' exon
O
H H O O
H H O P O
HO OH O
5' CH 2 N
7-methyl guanosine O
H H U... ...G
H H
b) G A
O OH 5' ...A G C ...CA GG... 3'
7
m Gppp N ... Cap
Lasso
5' end structure

...G
U G A
C ...CA GG... 3'
c) 5' ...AG

mRNA

U ...G
d) 5' ...AGGG... 3' G A
C ...CA

CH 2 Ade
O
H H O
H H H H
O OH OH O H H
O
O P O CH 2 Ade H O
O
O H H H H Gua CH 2 O P O
O
H H O O
O OH Gua CH 2 O P O
O P O CH 2 Ade O H H
O
O H H
H H O
Poly-A sequence H H O
Ade CH 2 O P O
O OH
O
To the 3' end
C. Spliceosome
Intron
Proteins snRNA snRNP U1 U2
+ U1
U1
+ U2 hnRNA U
U2 G A
snRNA
G
+ U4
U4 A
+ U5 U5 C A U 4/6
U5 5' exon G
G
+ U6 3' exon

U6
5' 3'
Spliceosome (schematic)

Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
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