Nucleic acid construct
The present invention provides a nucleic acid construct comprising the following structure: A-X-B in which A is nucleic acid sequence encoding a first polypeptide which comprises a first signal peptide; B is nucleic acid sequence encoding a second polypeptide which comprises a second signal peptide and X is a nucleic acid sequence which encodes a cleavage site, wherein the first signal peptide or the second signal peptide comprises one or more mutation(s) such that it has fewer hydrophobic amino acids.
1. A nucleic acid construct comprising the following structure:
A-X-B
in which
(a) A is nucleic acid sequence encoding a first polypeptide which comprises a first signal peptide attached to a first mature protein, the first signal peptide having a tripartite structure containing a hydrophobic core region (h-region) flanked by an n-region and a c-region,
(b) B is nucleic acid sequence encoding a second polypeptide which comprises a second signal peptide attached to a second mature protein, the second signal peptide having a tripartite structure containing a hydrophobic core region (h-region) flanked by an n-region and a c-region, and
(c) X is a nucleic acid sequence which encodes a cleavage site,
wherein the first signal peptide and the second signal peptide are derived from the same signal sequence having the same n- and c-regions, but the first signal peptide or the second signal peptide differ in the h-region, one signal peptide having 1, 2, 3, 4, or 5 amino acid deletions or substitutions in the h-region to remove or replace one or more hydrophobic amino acids compared to the other signal peptide such that the signal peptide with the amino acid deletions or substitutions has 1, 2, 3, 4, or 5 fewer hydrophobic amino acids in the h-region than the other signal peptide, and wherein differences between the first and the second signal peptides in the h-region are such that when the nucleic acid construct is expressed in an eukaryotic cell, there is differential relative expression of the first and second mature proteins.
2. The nucleic acid construct according to claim 1 , wherein the hydrophobic amino acid(s) is/are selected from the group consisting of Alanine (A), Valine (V), Isoleucine (I), Leucine (L), Methionine (M), Phenylalanine (F), Tyrosine (Y), and Tryptophan (W).
3. The nucleic acid construct according to claim 2 , wherein the hydrophobic amino acid(s) is/are selected from the group consisting of Valine (V), Isoleucine (I), Leucine (L), and Tryptophan (W).
4. The nucleic acid construct according to claim 1 , wherein the first and second polypeptides are both transmembrane proteins, and wherein there is differential relative expression of the first and second transmembrane proteins at the cell surface.
5. The nucleic acid construct according to claim 4 , wherein the first and second transmembrane proteins are both chimeric antigen receptors (CARs).
6. The nucleic acid construct according to claim 1 , wherein the cleavage site is a self-cleaving peptide, a furin cleavage site or a Tobacco Etch Virus cleavage site.
7. An expression vector comprising the nucleic acid construct according to claim 1 .
8. A retroviral vector or a lentiviral vector according to claim 7 .
9. An isolated eukaryotic cell comprising the nucleic acid construct according to claim 1 .
10. The isolated eukaryotic cell according to claim 9 which is a T cell or a natural killer (NK) cell.
11. The isolated eukaryotic cell according to claim 9 that is an isolated mammalian cell.