Chromosomal landing pads and related uses
Provided herein are methods for stable integration and/or expression of one or more recombinant polynucleotides in a host cell. The recombinant polynucleotides are typically integrated into the host genome at some native chromosomal integration sites. The integration can be mediated by homologous recombination or by using a hybrid recombinase targeting the specific chromosomal locations. The native chromosomal integration sites in the host cells, which support stable integration and strong transcription activities of foreign genes, are present within or adjacent to specific genes in the CHO genome, the ankyrin 2 gene (Ank2), cleavage and polydenylation specific factor 4 gene (Cpsf4), C-Mos gene, and Nephrocystin-1/Mal gene. Also provided are methods and nucleic acid molecules for inserting site-specific recombination sequences (chromosomal landing pads) into these specific chromosomal locations, engineered host cells containing chromosomal landing pads, methods and compositions (e.g., kits) therefore.
1. An ex vivo method for stable integration and expression of a heterologous polynucleotide in a Chinese Hamster Ovary (CHO) host cell, comprising inserting the heterologous polynucleotide into the genome of the host cell at a native chromosomal site located at or close to positions 239-240 of SEQ ID NO:4 for Nephrocystin-1/Mal gene.
2. The method of claim 1 , wherein insertion of the heterologous polynucleotide is mediated by homologous recombination or by a hybrid recombinase.
3. The method of claim 1 , wherein the heterologous polynucleotide encodes a polypeptide.
4. The method of claim 3 , wherein the polypeptide is a therapeutic protein or an industrial protein.
5. An ex vivo method for stably integrating a heterologous polynucleotide into the genome of a CHO cell, comprising:
(a) inserting a site-specific recombination sequence into the genome of the cell, wherein the insertion is at a native chromosomal insertion site located at or close to positions 239-240 of SEQ ID NO: 4 for Nephrocystin-1/Mal gene; and
(b) integrating by homologous recombination the heterologous polynucleotide into the genome of the cell at the inserted site-specific recombination sequence.
6. The method of claim 5 , wherein the native chromosomal insertion site supports stable integration of a foreign gene.
7. The method of claim 5 , wherein the site-specific recombination sequence is a first recognition sequence recognized by a phage integrase.
8. The method of claim 7 , wherein the phage integrase is phiC-31 integrase.
9. The method of claim 7 , wherein the first recognition sequence is an attP site or an attB site.
10. The method of claim 7 , wherein the heterologous polynucleotide is attached to a second recognition sequence of the phage integrase which is cognate to the first recognition sequence.
11. The method of claim 10 , wherein the second recognition sequence is an attB site or an attP site.
12. The method of claim 7 , wherein the integration occurs in the presence of the phage integrase.
13. The method of claim 12 , wherein the phage integrase is expressed from a vector introduced into the cell.
14. The method of claim 5 , wherein the heterologous polynucleotide comprises a target polypeptide-encoding sequence that is operably linked to a promoter sequence.