Methods of modulating nucleic acid stability and protein expression

1. A synthetic nucleic acid which encodes a protein in a mammalian host cell, wherein at least one optimal or non-optimal codon in a wild type nucleic acid encoding the protein has been replaced respectively with one or more non-optimal codons or optimal codons encoding the same amino acid, the synthetic nucleic acid being capable of expressing the protein at a level that is at least about 10% different compared to that expressed by the wild type nucleic acid in an in vitro mammalian cell culture system under identical conditions, and wherein the optimal codons are selected from the group consisting of get (Alanine), ggt (Glycine), gtc (Valine), ttg (Leucine), gtt (Valine), cca (Proline), act (Threonine), tct (Serine), tcc (Serine), gaa (Glutamic Acid), cgt (Arginine), caa (Glutamine), att (Isoleucine), aga (Arginine), and tgt (Cysteine); and the non-optimal codons are selected from the group consisting of ggc (Glycine), tgg (Tryptophan), atg (Methionine), tgc (Cysteine), ccc (Proline), gtg (Valine), cgc (Arginine), gag (Glutamic Acid), cag (Glutamine), agc (Serine), and ctg (Leucine);

wherein the replacement of one or more codons from the nucleic acid sequence with one or more optimal codons increases stabilization of mRNA and mRNA half-life or with one or more non-optimal codons decreases stabilization of mRNA and mRNA half-life transcribed from the nucleic acid sequence compared to the nucleic acid sequence prior to replacement.

2. The synthetic nucleic acid sequence of claim 1 , wherein the synthetic nucleic sequence is capable of expressing the protein at a level which is at least about 50% different compared to that expressed by the wild type nucleic acid in an in vitro mammalian cell culture system under identical conditions.

3. The synthetic nucleic acid sequence of claim 1 , wherein the synthetic nucleic sequence is capable of expressing the protein at a level which is at least about 75% different compared to that expressed by the wild type nucleic acid in an in vitro mammalian cell culture system under identical conditions.

4. The synthetic nucleic acid sequence of claim 1 , wherein one or more of the optimal codons is replaced with a non-optimal codon encoding the same amino acid as the replaced codon so that the synthetic nucleic acid sequence has less than about 40% optimal codons.

5. The synthetic nucleic acid sequence of claim 1 , wherein one or more of the non-optimal codons is replaced with an optimal codon encoding the same amino acid as the replaced codon so that the synthetic nucleic acid sequence has more than about 70% optimal codons.

6. The synthetic nucleic acid of claim 1 , wherein the mammalian cell is a CHO (Chinese Hamster Ovary) cell.

7. The synthetic nucleic acid of claim 1 , comprising in vitro transcribed mRNA.

8. The synthetic nucleic acid of claim 1 , comprising DNA.

9. An expression vector comprising the synthetic nucleic acid of claim 1 .

10. The expression vector of claim 9 , being a mammalian expression vector.

11. A method of modulating the expression of a recombinant protein in a mammalian host cell, the method comprising:

identifying optimal and non-optimal codons in a nucleic acid sequence that encodes the protein,

replacing one or more of the optimal codons with a non-optimal codon encoding the same amino acid as the replaced codon or replacing one or more of the non-optimal codons with an optimal codon encoding the same amino acid,

and transfecting the mammalian host cell with the nucleic acid with the replaced codon, wherein the replacement of the one or more codons from the nucleic acid sequence modulates expression of the recombinant protein in the host cell at least about 10% compared to the nucleic sequence prior to replacement, and wherein the optimal codons are selected from the group consisting of get (Alanine), ggt (Glycine), gtc (Valine), ttg (Leucine), gtt (Valine), cca (Proline), act (Threonine), tct (Serine), tcc (Serine), gaa (Glutamic Acid), cgt (Arginine), caa (Glutamine), att (Isoleucine), aga (Arginine), and tgt (Cysteine); and the non-optimal codons are selected from the group consisting of ggc (Glycine), tgg (Tryptophan), atg (Methionine), tgc (Cysteine), ccc (Proline), gtg (Valine), cgc (Arginine), gag (Glutamic Acid), cag (Glutamine), agc (Serine), and ctg (Leucine);

wherein the replacement of one or more codons from the nucleic acid sequence with one or more optimal codons increases stabilization of mRNA and mRNA half-life or with one or more non-optimal codons decreases stabilization of mRNA and mRNA half-life transcribed from the nucleic acid sequence compared to the nucleic acid sequence prior to replacement.

12. The method of claim 11 , wherein the replacement of the one or more codons from the nucleic acid sequence increases expression of the recombinant protein in the host cell at least about 10% compared to the nucleic acid sequence prior to replacement.

13. The method of claim 12 , wherein the replacement of the one or more codons from the nucleic acid sequence increases stabilization of mRNA transcribed from the nucleic acid sequence compared to the nucleic acid sequence prior to replacement.

14. The method of claim 11 , wherein the replacement of the one or more codons from the nucleic acid sequence decreases expression of the recombinant protein in the host cell at least about 10% compared to the nucleic acid sequence prior to replacement.

15. The method of claim 14 , wherein the replacement of the one or more codons from the nucleic acid sequence decreases stabilization of mRNA transcribed from the nucleic acid sequence compared to the nucleic acid sequence prior to replacement.

16. The method of claim 11 , wherein the mammalian host cell is a CHO (Chinese Hamster Ovary) cell.