E. coli CAP +cAMP + DNA

HTH motif

cAMP

ATATAA = consensus sequence of TATA box

start point at: Py2CA Py5

TFIID

Human TBP complexed at TATA box of DNA

G

G

C

A

TA T

A

T A

T

C

5'

3'

octamer CAAT GC TATA start point

DNA binding motif of steroid receptorsZn fingers

Other DNA binding motifsHelix-turn-helixHelix-loop-helix

Additional motif often present in transcription factorsLeucine zippers 

 

-Cys-X2-4-Cys-X3-Phe-X5-Leu-X2-His-X3-His-

The zinc finger motif is:

C-terminalN-terminal

Zn finger fragment bound to DNA

Hormone binding and dimerization regions vary from 5-15%

C-terminal

N-terminal

finger

DNA binding

dimerization

GLUCOCORTICOID RECEPTOR FRAGMENT BOUND TO DNA

homeodomain

Helix-turn-helix binding motif

#3, C-terminal

#1, N-terminal

#3

#2

#1

bHLH DNA binding motif of transcription factor MyoD

basic region binding DNA

helix 1

helix 2

CREB-DNA complex

Leu selected in zipper domain

Arg selected in DNA-binding domain

Chains: blue = c-Fos, green = c-Jun

Residues: red = Leu, purple = Arg

Human protooncogenes c-Jun:c-Fos heterodimer

HN

N N

N

O

H2N

N

N N

N

O

H2N

HN

N N

N

OH

H2N

N

N N

N

O

HN

H

H

N N

O

O

H

HN

N N

N

O

H2N

N

N N

N

O

H2N

HN

N N

N

OH

H2N

N

N N

N

O

HN

H

H

N N

O

O

H

HN

N N

N

O

H2N

N

N N

N

O

H2N

HN

N N

N

OH

H2N

N

N N

N

O

HN

H

H

N N

O

O

H

H3C

Keto-enol tautomerization of Gua

keto form (normal)

enol form

pairing properties of enol

Point mutation, transition

pyrimidinepyrimidine

purinepurine

Point mutation, transversion

pyrimidinepurine

purinepyrimidine

GT GC + AT

GC CG, TA AT, GC TA

nonsense mutation occurs when a termination codon is generated

missense mutation occurs when a different amino acid is coded

GT GC + AT

One round of replication on mismatched strands “fixes” the mutation.

3'-G-p-G-p-G-p-G-p-G-p-G-5' 3'-G-p-G-p G-p-G-p-G-p-G-5'5'-C-p-C p-C-OH 5'-C-p-C-p-C-OH

p-C

G-p

Mechanism for frameshift mutations

ATA GCA ACC GGC CTT ACA AAT TC

ATA GCA ACC GCC TTA CAA ATT C

Change of reading frame following the location of a deletion

insertion deletion

LOCUS tRNA WILD-TYPE

codon/anticodon

SUPPRESSOR

anticodon/codon

supD(su1) Ser UCG CGA CUA UAG

supE(su2) Gln CAG CUG CUA UAG

supF(su3) Tyr UAC GUA CUA UAG

supC(su4) Tyr AAC GUA UUA UAA

supG(su5) Lys AAA UUU UUA UAA

supU(su7) Trp UGG CCA UCA UGA

U

U

G

G G

G

G

Bacterial nonsense suppressors

O

O

OOP

O

O

O

HN

O

O

OO

CH3

CH3HN

O

thymine-thymine dimer

T T