Permanent epigenetic gene silencing

1. A product comprising a combination of artificial transcription repressors (ATRs) selected from the group consisting of: (a) and (b), and (a) and (c), or polynucleotides encoding therefor, wherein:

(a) is an ATR comprising a DNA-binding domain operably linked to a Krüppel-associated box (KRAB) domain or homologue thereof;

(b) is an ATR comprising a DNA-binding domain operably linked to a DNA methyltransferase 3A (DNMT3A) domain or homologue thereof; and

(c) is an ATR comprising a DNA-binding domain operably linked to a DNA (cytosine-5)-methyltransferase 3-like (DNMT3L) domain or homologue thereof.

2. The product of claim 1 , wherein:

(i) the KRAB domain or homologue thereof comprises an amino acid sequence that has at least 60% identity to any one of SEQ ID NOs: 1-7;

(ii) the DNMT3A domain or homologue thereof comprises an amino acid sequence that has at least 60% identity to SEQ ID NO: 8;

(iii) the DNMT3L domain or homologue thereof comprises an amino acid sequence that has at least 60% identity to SEQ ID NO: 11; and/or

(iv) the DNA-binding domain of (a), (b), or (c) comprises a domain independently selected from a transcription-activator like effector (TALE) DNA-binding domain, a zinc finger domain, a tetracycline-controlled repressor (tetR) DNA-binding domain, a meganuclease or a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas system.

3. The product of claim 1 , wherein the polynucleotides encoding the ATRs are in the form of a single vector or are comprised within separate vectors.

4. A method of gene therapy comprising transfecting a cell with the polynucleotides encoding the two or more ATRs as defined in claim 3 , optionally wherein the transfection is carried out ex vivo.

5. The product of claim 1 , further comprising a separate effector protein that is not operably linked to a DNA-binding domain, or polynucleotide encoding therefor, wherein the separate effector protein that is not operably linked to a DNA-binding domain comprises a domain selected from groups (a), (b), (c) or (d):

(a) a KRAB domain or homologue thereof;

(b) a DNMT3A, DNMT3B or DNMT1 domain or homologue thereof;

(c) a DNMT3L domain or homologue thereof; and

(d) a SETDB1 domain or homologue thereof.

6. The product of claim 1 in the form of a pharmaceutical composition further comprising a pharmaceutically acceptable carrier, diluent or excipient.

7. A cell comprising the ATRs as defined in claim 1 .

8. A cell wherein said cell is a descendant of the cell of claim 7 .

9. The product of claim 1 comprising an artificial transcription repressor (ATR) comprising a DNA-binding domain operably linked to a KRAB domain or homologue thereof, an ATR comprising a DNA-binding domain operably linked to a DNMT3L domain or homologue thereof, and an ATR comprising a DNA-binding domain operably linked to a DNMT3A domain or homologue thereof, or polynucleotides encoding therefor.

10. The product of claim 1 comprising an artificial transcription repressor (ATR) comprising a DNA-binding domain operably linked to a KRAB domain or homologue thereof, and an ATR comprising a DNA-binding domain operably linked to a DNMT3L domain or homologue thereof, or polynucleotides encoding therefor.

11. The product of claim 1 comprising an artificial transcription repressor (ATR) comprising a DNA-binding domain operably linked to a KRAB domain or homologue thereof, and an ATR comprising a DNA-binding domain operably linked to a DNMT3A domain or homologue thereof, or polynucleotides encoding therefor.

12. A method of gene therapy comprising administering the product of claim 1 to a subject, wherein the ATRs are administered simultaneously, sequentially or separately.

13. The method of claim 12 , wherein:

(i) transient expression of the two or more ATRs in a cell silences a target gene;

(ii) delivery of the two or more ATRs to a cell permanently silences a target gene;

(iii) delivery of the two or more ATRs to a cell permanently silences a target gene in the cell's progeny; and/or

(iv) the DNA-binding domains of the different ATRs are selected to bind to binding sites that are separated by 0-30 bp, optionally wherein the DNA-binding domains are TALE DNA-binding domains or CRISPR/Cas systems.

14. A method of silencing a target gene comprising the step of administering the product of claim 1 to a cell.

15. An artificial transcription repressor (ATR) comprising a DNA-binding domain operably linked to two or more domains selected from groups (a), (b), or (c); wherein the two or more domains comprise: (a) and (b), or (a) and (c); wherein:

(a) is a Krüppel-associated box (KRAB) domain or homologue thereof;

(b) is a DNA methyltransferase 3A (DNMT3A) domain or homologue thereof; and

(c) is a DNA (cytosine-5)-methyltransferase 3-like (DNMT3L) domain or homologue thereof;

optionally wherein the DNA-binding domain comprises a transcription-activator like effector (TALE) DNA-binding domain, a zinc finger domain, a tetracycline-controlled repressor (tetR) DNA-binding domain, a meganuclease, or a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas system.

16. A polynucleotide encoding the ATR of claim 15 .

17. A cell comprising the ATR as defined in claim 15 .

18. A cell wherein said cell is a descendant of the cell of claim 17 .

19. The ATR of claim 15 , wherein the ATR comprises a DNA-binding domain operably linked to a KRAB domain or homologue thereof, a DNTM3A domain or homologue thereof, and a DNMT3L domain or homologue thereof.

20. The ATR of claim 15 , wherein the ATR comprises a DNA-binding domain operably linked to a KRAB domain or homologue thereof, and a DNMT3L domain or homologue thereof.

21. The ATR of claim 15 , wherein the ATR comprises a DNA-binding domain operably linked to a KRAB domain or homologue thereof, and a DNTM3A domain or homologue thereof.

22. A product comprising two or more different artificial transcription repressors (ATRs), or polynucleotides encoding therefor, wherein the two or more different ATRs individually comprise a DNA-binding domain operably linked to two or more domains selected from groups (a), (b), or (c); wherein the two or more domains comprise: (a) and (b), or (a) and (c); wherein:

(a) is a Krüppel-associated box (KRAB) domain or homologue thereof;

(b) is a DNA methyltransferase 3A (DNMT3A) domain or homologue thereof; and

(c) is a DNA (cytosine-5)-methyltransferase 3-like (DNMT3L) domain or homologue thereof;

optionally wherein the DNA-binding domains of the two or more different ATRs are individually selected from the group consisting of a transcription-activator like effector (TALE) DNA-binding domain, a zinc finger domain, a tetracycline-controlled repressor (tetR) DNA-binding domain, a meganuclease, and a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas system.

23. A cell comprising the ATRs as defined in claim 22 .

24. A cell wherein said cell is a descendant of the cell of claim 23 .