Protein expression enhancing polypeptides

1. A fusion protein comprising:

(1) a protein expression enhancing polypeptide (PEEP) domain linked to (2) a target protein binding domain,

wherein said protein expression enhancing polypeptide (1) is selected from the group consisting of:

(a) an isolated J domain of a J protein;

(b) a J domain analog polypeptide comprising the amino acid sequence of formula I:

X1-X2-X3-X4-X5-X6-X7-X8-X9 (SEQ ID NO:47), wherein:  (I)

X1 is isoleucine (I), leucine (L), valine (V), alanine (A), or methionine (M);

X2 and X3 are each independently any amino acid with the proviso that one or both are K or R;

X4 is any amino acid or X4 may be absent when X1 through X3 are present and

X5 through X9 are present;

X5 is tyrosine (Y), tryptophan (W), or phenylalanine (F);

X6 and X7 are each independently any amino acid with the proviso that one or both are lysine (K) or arginine (R); or either one of X6 and X7 may be absent when the other is K or R and when X1 through X5 are present and X8 and X9 are present; and

X8 and X9 are any amino acid with the proviso that one or both are leucine (L) or alanine (A); or one of X8 and X9 may be absent when the other is L or A and when X1 through X7 are present; and

(c) a decapeptide selected from the group consisting of:

IKKAYKLALQ (SEQ ID NO:49),

IKKAYRLALQ (SEQ ID NO:50),

IKKAYRKALQ (SEQ ID NO:51), and

IKKAYRKLLQ (SEQ ID NO:52);

wherein said target protein binding domain (2) is a protein or binding domain thereof that specifically binds a target protein of interest; and

wherein co-expression of said fusion protein with said target protein of interest that is bound by said target protein binding domain of said fusion protein results in an enhanced level of expression of said target protein of interest compared to the level of expression in the absence of said fusion protein.

2. The fusion protein according to claim 1 , wherein the protein expression enhancing polypeptide (1) consists of an isolated J domain of a J protein.

3. The fusion protein according to claim 2 , wherein the isolated J domain is an isolated J domain of an ERdj protein, a large T antigen of SV40, or a mammalian cysteine string protein alpha (CSP-α).

4. The fusion protein according to claim 2 , wherein the isolated J domain is an isolated J domain of an Erdj protein selected from Erdj1, Erdj2, Erdj3, Erdj4, Erdj5, Erdj6 and Erdj7.

5. The fusion protein according to claim 4 , wherein the isolated J domain is an isolated J domain of Erdj3.

6. The fusion protein according to claim 1 , wherein the protein expression enhancing polypeptide is selected from the group consisting of:

I-K-K-A-Y-R-K-L-A (SEQ ID NO:48),

I-R-K-A-Y-R-K-L-S-L-T-L (SEQ ID NO:83),

I-K-K-Q-Y-R-L-L-S-L-K-Y (SEQ ID NO:84),

I-K-K-A-F-H-K-L-A-M-K-Y (SEQ ID NO:85),

I-R-Q-A-F-K-K-L-A-L-K-L (SEQ ID NO:86),

I-I-K-A-Y-R-K-L-A-L-Q-W (SEQ ID NO:87),

I-A-R-A-Y-R-Q-L-A-R-R-Y (SEQ ID NO:88),

I-K-R-A-Y-R-R-Q-A-L-R-Y (SEQ ID NO:89),

I-K-K-S-Y-R-K-L-A-L-K-Y (SEQ ID NO:90), and

I-K-K-A-Y-K-R-L-A-M-K-Y (SEQ ID NO:91).

7. The fusion protein according to claim 1 , wherein the protein expression enhancing polypeptide is a J domain analog polypeptide, wherein said J domain analog polypeptide comprises the amino acid sequence of formula I.

8. The fusion protein according to claim 7 , wherein said J domain analog polypeptide comprises the amino acid sequence (SEQ ID NO:326) wherein:

X1 is I, L, V, A, or M;

the dipeptide X2-X3 is selected from the group consisting of: KR, KK, RK, RR, AK, AR, KA, IK, NK, KQ, RQ, and RD;

X4 is A, S, T, R, Q, E, F, C, or I;

X5 is Y or F;

the dipeptide X6-X7 is selected from the group consisting of: KR, KK, RK, RR, RQ, FR, RL, KL, HK, LK, QK, and KV; and

the dipeptide X8-X9 is selected from the group consisting of: LA, LL, AL, AA, LC, LV, QA, KA, LS, LI, LY, and RA.

9. The fusion protein according to claim 1 , wherein said protein expression enhancing polypeptide (1) comprises one of the following amino acid sequences:

Amino Acid Sequence

Sequence Identifier

123456789012345

SEQ ID NO: 48

IKKAYRKLA

SEQ ID NO: 49

IKKAYKLALQ

SEQ ID NO: 50

IKKAYRLALQ

SEQ ID NO: 51

IKKAYRKALQ

SEQ ID NO: 52

IKKAYRKLLQ

SEQ ID NO: 53

IKKYRKLA

SEQ ID NO: 54

IKKAYKLA

SEQ ID NO: 55

IKKAYRLA

SEQ ID NO: 56

IKKAYRKA

SEQ ID NO: 57

LKKAYRKLA

SEQ ID NO: 58

VKKAYRKLA

SEQ ID NO: 59

MKKAYRKLA

SEQ ID NO: 60

AKKAYRKLA

SEQ ID NO: 61

IAKAYRKLA

SEQ ID NO: 62

IKAAYRKLA

SEQ ID NO: 63

IKKRYRKLA

SEQ ID NO: 64

IKKSYRKLA

SEQ ID NO: 65

IKKQYRKLA

SEQ ID NO: 66

IKKEYRKLA

SEQ ID NO: 67

IKKFYRKLA

SEQ ID NO: 68

IKKCYRKLA

SEQ ID NO: 69

IKKAFRKLA

SEQ ID NO: 70

IKKAWRKLA

SEQ ID NO: 71

IKKAYRKQA

SEQ ID NO: 72

IKKAYRKMA

SEQ ID NO: 73

IKKAYRKIA

SEQ ID NO: 74

IKKAYRKAA

SEQ ID NO: 75

IKKAYRKVA

SEQ ID NO: 76

IKKAYRKRA

SEQ ID NO: 77

IKKAYRKLM

SEQ ID NO: 78

IKKAYRKLI

SEQ ID NO: 79

IKKAYRKLV

SEQ ID NO: 80

IKKAYRKLC

SEQ ID NO: 81

IKKAYRKLS

SEQ ID NO: 82

IKKAYRKLY

SEQ ID NO: 83

IRKAYRKLSLTL

SEQ ID NO: 84

IKKQYRLLSLKY

SEQ ID NO: 85

IKKAFHKLAMKY

SEQ ID NO: 86

IRQAFKKLALKL

SEQ ID NO: 87

IIKAYRKLALQW

SEQ ID NO: 88

IARAYRQLARRY

SEQ ID NO: 89

IKRAYRRQALRY

SEQ ID NO: 90

IKKSYRKLALKY

SEQ ID NO: 91

IKKAYKRLAMKY.

10. The fusion protein according to claim 1 , wherein the target protein binding domain (2) is an antibody or an antigen-binding fragment thereof, an antibody binding protein, a ligand binding domain of a receptor protein, a protein ligand of a receptor protein, a protein antigen that is bound by an antibody or an antigen-binding fragment thereof, or a PDZ domain.

11. The fusion protein according to claim 10 , wherein the target protein binding domain (2) is an antibody binding protein.

12. The fusion protein according to claim 11 , wherein the antibody binding protein is an Fc binding protein.

13. The fusion protein according to claim 12 , wherein the Fc binding protein is Protein A, Protein G, or a viral gE protein.

14. The fusion protein according to claim 11 , wherein the antibody binding protein is Protein L.

15. The fusion protein according to claim 10 , wherein said target protein binding domain (2) is a ligand binding domain of a receptor protein, wherein the receptor protein is a cytokine receptor.

16. The fusion protein according to claim 10 , wherein said target protein binding domain (2) is a protein ligand of a receptor protein, wherein the protein ligand is a cytokine.

17. An isolated nucleic acid molecule comprising a nucleic acid sequence encoding a fusion protein according to claim 1 or claim 9 .

18. A nucleic acid vector molecule comprising the isolated nucleic acid molecule according to claim 17 .

19. A host cell comprising the nucleic acid vector molecule according to claim 18 .

20. A method of expressing a fusion protein comprising culturing a host cell according to claim 19 under conditions sufficient to produce the fusion protein.

21. A method of enhancing the expression of a target protein of interest expressed by a host cell comprising transfecting the host cell with an expression vector comprising a structural gene encoding a fusion protein according to claim 1 , and culturing said transfected host cell under conditions causing the co-expression of said fusion protein encoded by said structural gene and of said target protein of interest.

22. A method of enhancing the expression of a target protein of interest comprising the steps of:

1) constructing a recombinant gene encoding a fusion protein according to claim 1 wherein the target protein binding domain (2) of the fusion protein binds said target protein of interest;

2) inserting the recombinant gene into an expression vector to form a recombinant expression vector wherein said recombinant gene sequence is operably linked to a transcriptional promoter sequence;

3) transfecting said recombinant expression vector into host cells that are compatible with said promoter sequence; and

4) culturing said transfected host cells under conditions that permit co-expression of said fusion protein encoded by said recombinant gene and of said target protein of interest.

23. A method of restoring a secreted protein function in cells of a mammalian subject that are deficient in the secretion of a native secreted protein that provides said secreted protein function comprising inserting into cells of the subject an exogenous nucleic acid molecule encoding a fusion protein according to claim 1 wherein the target protein binding domain (2) of the fusion protein binds the native secreted protein, wherein expression of the fusion protein and the native secreted protein in the cells enhances secretion of said native protein to provide said protein function to the cells of the subject.

24. The method according to claim 23 , wherein the subject has a disease associated with the deficient secretion of the native protein in the subject.

25. The method according to claim 24 , wherein said disease is selected from the group consisting of a prion-associated disease, Alzheimer's disease, Parkinson's disease, Huntington's disease, cystic fibrosis (CF), and α1-antitrypsin (AAT) deficiency.

26. The method according to claim 25 , wherein the subject is a human subject deficient in the secretion of cystic fibrosis transmembrane conductance regulator protein and the disease is cystic fibrosis.

27. The method according to claim 25 , wherein the subject is a human subject deficient in secretion of AAT and the disease is AAT deficiency.