TALNs are Restriction enzymes which use as Genome editing tool,

1. (TALEN’s)
Muhammad Mujahid ID: F2019253023

2.  Transcription activator-like effector nucleases (TALEN)
are restriction enzymes that can be engineered to cut
specific sequences of DNA.
 They are made by fusing of:
i. DNA-binding domain (TAL effector).
ii. DNA cleavage domain (a nuclease which cuts DNA
strands).

3. TALEs
• TALEs – Transcription Activator-Like Effector proteins
produced by certain plant pathogenic bacteria, Xanthomonase
spp.
• Act as effectors during pathogenesis.
• It contain:
i. NLS (nuclear localization sequence).
ii. N-terminal translocation signal.
iii. Transcriptional activator domain.
iv. Central repeat domain.
• Contain 17 to 18 tandem repeats of a 33-35 amino acid motif
that can recognise a single base through two di-variant
residues
•DNA binding specificity is determined by the amino acids at
positions 12 and 13 within each repeat which is called Repeat
Variable Diresidue (RVD) .

5. 5
Structure and DNA binding code of TALEs
NG = T
HD = C
NI = A
NN = G or A
DNA binding code
N’ C’
Central repeat domain
ADNLS
L T P E Q V V A I A S H D G G K Q A L E T V Q R L L P V L C Q A H G
1 3412 13
TS
Repeats (1.5 to 33.5)
Repeat variable diresidue (RVD)
12 13

6. 6
How to engineer TALEs?
N’
TS
C’
ADNLS
HD HD HD NI NI NI NG NG NG NK NI NG HD NK
DNA Target TCCCAAATTTGATCG
Engineered central repeat domain
= CHD
NI
NG
NK
= A
= T
= G

7. TALENs

8. G G A T G N N N N N N N N N N N N N N N N N N N
C C T A C N N N N N N N N N N N N N N N N N N N
5’
3’
3’
5’
Nuclease
DNA-binding
21-Nov-16
8
 Flavobacterium okeanokoites
 N-terminal: DNA-binding domain
 C-terminal: nonspecific DNA-cleavage activity

9. Fok I nucleases
21-Nov-16
9

12.  Transcription activator like Effector Nucleases (TALENs)
is a synthetic modified Restriction Enzyme.
 It consist on TALEs (proteins) and Nuclease enzyme
(Fok 1).
 It use as tool for Genome Editing.
 In 2011, named “The methods of the Year”