5' splice site

3' splice site

(YYYYY) n

Branch Point Polypyrimidine Tract

~40 nts

YNYUR A Y

Intron

Exon

A

B

Figure 1

Intron de�nition Exon de�nition

Splice-site recognition

Exon A Exon B Exon A Exon B

Figure 2

A

Splice-site recognition

Splice-site Pairing

U2

(Long Intron)(Short Intron)

B

U1 U2 A n o x E

B

n o

x E

U1 2 U

2 U

A n o x E

B

n o

x E

U1

1 U

2 U

U2 U1 U1

Spliceosomal Assembly

Splice-site Pairing

Figure 3

hnRNPsFox andOthers

ESE

SRProtein

U1U2

ISE

U1U2

ESSISShnRNPPTB and

Others

A

B

5' splice site

Intron Exon

S S I

Figure 4

Activating Secondary Structure Inhibitory Secondary Structure

ESE

Figure 5

variable intron length

variable exon length

Exon/intron architecture

Local Secondary Structure

3' splice site

A (YYYYY)n

5' splice site

ESEESSISE ISS

Branch PointPolypyrimidine Tract

~40 nts

Promoter Poly-adenylation site

Figure 6

ISS ISS ISS ISE ESE C U ESS

Inhibitory Secondary Structures

Position 6 C to U SMN2 Switch

3’ Splice Site 5’ Splice Site

variable intron length

Silencing Elements

Enhancing Elements

Exon 7