Nucleotides and aptamers containing boronic acid groups having biased binding to glycosylated proteins, and uses thereof
The present disclosure encompasses oligonucleotide aptamers selectively binding a target glycosylated polypeptide or protein, and having biased affinity for the glycan through a boronic acid linked to a nucleosidic base of a nucleotide(s). The disclosure further encompasses methods for isolating an aptamer(s) selectively binding a target glycosylated polypeptide, where, from a population of randomized oligonucleotides that have at least one nucleotide having a boronic acid label linked to a base, is selected a first subpopulation of aptamers binding to the target glycosylated polypeptide or protein. This subpopulation is then amplified without using boronic acid-modified TTP, and amplification products not binding to a target glycosylated polypeptide or protein are selected. The second subpopulation of aptamers is then amplified using boronic acid-modified TTP to provide a population of boronic acid-modified aptamers capable of selectively binding to a glycosylation site of a target polypeptide or protein. Other aspects of the disclosure encompass methods for the use of the modified aptamers to detect glycosylated species of a polypeptide or protein.
1. A nucleotide monomer having the formula:
wherein R 1 is selected from the group consisting of: a monophosphate ester, a diphosphate ester, and a triphosphate ester;
wherein R 2 and R 3 are each individually selected from H, or OH;
wherein R 4 is a base selected from the group consisting of: adenine, cytosine, guanine, thymine, hypoxanthine and uracil; and
wherein R 5 is a boronic acid other than an unsubstituted phenylboronic acid having the structure:
wherein R 4 and R 5 are linked by a a spacer, wherein said spacer is the product of a Click chemistry reaction between an azide group of a linker covalently attached to the boronic acid (R 5 ) and a reactive alkynyl group of a tether which has a second alkynyl group conjugated to the base (R 4 ).
2. The nucleotide monomer of claim 1 , wherein the second alkynyl group is an ethynyl group.
3. The nucleotide monomer of claim 1 , wherein the tether has the formula
—C≡C—CH 2 —CH 2 —CO—NH—CH 2 —C≡C—.
4. The nucleotide monomer of claim 1 , wherein R 4 is uracil, R 2 is OH, and R 3 is H.
5. The nucleotide monomer of claim 1 , wherein R 5 is a boronic acid selected from the group consisting of: a substituted phenylboronic acid, a naphthalenylboronic acid, a quinolinylboronic acid, a pyridinylboronic acid, a furanylboronic acid, a thiophenylboronic acid, an indolylboronic acid a 1,8-naphthalimide-based boronic acid, an α-acetaminoalkylboronic acid, a quinolin-4-ylboronic acid, a quinolin-5-ylboronic acid, a quinolin-8-ylboronic acid, a pyridinylboronic acid, a furan-2-ylboronic acid, and a thiophen-2-ylboronic acid.
6. The nucleotide monomer of claim 5 , wherein R 5 is selected from the group consisting of the structures:
7. A nucleotide monomer having the formula:
8. An oligonucleotide comprising at least one nucleotide monomer having the formula:
wherein R 1 is a monophosphate ester;
wherein R 2 and R 3 are each individually selected from H, or OH;
wherein R 4 is a base selected from the group consisting of: adenine, cytosine, guanine, thymine, inosine and uracil;
wherein R 5 is a boronic acid other than an unsubstituted phenylboronic acid having the structure:
wherein R 4 and R 5 are linked by a spacer, wherein said spacer is the product of a Click chemistry reaction between an azide group of a linker covalently attached to the boronic acid (R 5 ) and a reactive alkynyl group of a tether which has a second alkynyl group conjugated to the base (R 4 ).
9. The oligonucleotide of claim 8 , wherein R 4 is uracil, R 2 is OH, and R 3 is H.
10. The oligonucleotide of claim 8 , wherein R 5 is a boronic acid selected from the group consisting of: a substituted phenylboronic acid, a naphthalenylboronic acid, a quinolinylboronic acid, a pyridinylboronic acid, a furanylboronic acid, a thiophenylboronic acid, an indolylboronic acid, a 1,8-naphthalimide-based boronic acid, an α-acetaminoalkylboronic acid, a quinolin-4-ylboronic acid, a quinolin-5-ylboronic acid, a quinolin-8-ylboronic acid, a pyridinylboronic acid, a furan-2-ylboronic acid, and a thiophen-2-ylboronic acid.
11. The oligonucleotide of claim 8 , wherein the boronic acid is a fluorescent boronic acid.
12. The oligonucleotide of claim 11 , wherein the fluorescent boronic acid is selected from the group consisting of the structures:
13. A method of isolating an aptamer having selective affinity for a target polypeptide and a glycan thereon, comprising:
(a) selecting a first subpopulation of aptamers binding to a target glycosylated polypeptide or protein from a population of randomized oligonucleotides, wherein each oligonucleotide of the population of randomized oligonucleotides includes at least one nucleotide having a boronic acid label linked to a base thereon, wherein said at least one nucleotide monomer has the formula:
wherein R 1 is a monophosphate ester;
wherein R 2 and R 3 are each individually selected from H, or OH;
wherein R 4 is a base selected from the group consisting of: adenine, cytosine, guanine, thymine, inosine and uracil;
wherein R 5 is a boronic acid other than an unsubstituted phenylboronic acid having the structure:
wherein R 4 and R 5 are linked by a spacer, wherein said spacer is the product of a Click chemistry reaction between an azide group of a linker covalently attached to the boronic acid (R 5 ) and a reactive alkynyl group of a tether which has a second alkynyl group conjugated to the base (R 4 ), and wherein the aptamer has selective affinity for a target polypeptide and a glycosylation chain thereon;
(b) amplifying the first subpopulation of aptamers without using boronic acid-modified TTP, and selecting from the amplification products thereof a second subpopulation of aptamers not binding to a glycosylated species of the target polypeptide or protein; and
(c) amplifying the second subpopulation of aptamers using boronic acid-modified TTP, thereby providing a population of boronic acid-modified aptamers capable of selectively binding to a glycosylation site of a target polypeptide or protein.
14. The method of claim 13 , further comprising a counter-selection step, wherein the counter-selection step comprises identifying aptamers capable of selectively binding to a solid support not having a target polypeptide bound thereto, a deglycosylated target polypeptide or protein, or a cross-reacting non-targeted polypeptide or proteins.
15. The method of claim 13 , wherein step (a) comprises:
(a1) amplifying a library of randomized oligonucleotides, wherein each oligonucleotide includes at least one nucleotide having a boronic acid label linked to a base thereon;
(a2) contacting the library with a glycosylated target polypeptide or protein under conditions whereby a subpopulation of the library of aptamers selectively binds to a glycosylation site of the target polypeptide;
(a3) isolating target polypeptides or proteins having the subpopulation of aptamers bound thereto, and eluting the subpopulation of aptamers from the target polypeptide;
(a4) amplifying the eluted subpopulation of aptamers; and
(a5) repeating steps (a2)-(a4), thereby isolating a first subpopulation of aptamers from the amplified library from step (a1), wherein the aptamers are capable of binding a glycosylation site of the target polypeptide.
16. The method of claim 13 , further comprising:
(i) inserting a population of aptamers isolated in step c into a vector, and isolating clones thereof;
(ii) identifying a plurality of aptamer clones, wherein each aptamer has a nucleotide sequence differing from the sequences of the other aptamers;
(iii) determining the dissociation constants of the individual selected aptamers and the target glycosylated polypeptide;
(iv) comparing the dissociation constants of the aptamer sequences to the dissociation constants of a control aptamer not having a boronic acid thereon; and
(v) selecting one or more aptamers having a lower dissociation constant than the control, whereby the selected aptamers have enhanced selective affinity for a glycosylated site of the target polypeptide compared to control aptamers having an identical nucleotide sequence to that of the selected aptamers but not having a boronic acid group thereon.
17. The method of claim 13 , wherein the target polypeptide is immobilized on a solid support.
18. The method of claim 13 , wherein R 4 is uracil, R 2 is OH, and R 3 is H.
19. The method of claim 13 , wherein R 5 is a boronic acid selected from the group consisting of: a substituted phenylboronic acid, a naphthalenylboronic acid, a quinolinylboronic acid, a pyridinylboronic acid, a furanylboronic acid, a thiophenylboronic acid, an indolylboronic acid, a 1,8-naphthalimide-based boronic acid, an α-acetaminoalkylboronic acid, a quinolin-4-ylboronic acid, a quinolin-5-ylboronic acid, a quinolin-8-ylboronic acid, a pyridinylboronic acid, a furan-2-ylboronic acid, and a thiophen-2-ylboronic acid.
20. The method of claim 13 , wherein the at least one nucleotide having a boronic acid label modified base thereon comprises a fluorescent boronic acid selected from the group having the formulas:
21. A method of detecting a glycosylated species of a target polypeptide, comprising:
(a) providing a target polypeptide;
(b) contacting the target polypeptide with a first aptamer comprising at least one nucleotide having a boronic acid label linked to a base thereon, wherein the at least one nucleotide monomer has the formula:
wherein R 1 is a monophosphate ester;
wherein R 2 and R 3 are each individually selected from H, or OH;
wherein R 4 is a base selected from the group consisting of: adenine, cytosine, guanine, thymine, inosine and uracil;
wherein R 5 is a boronic acid other than an unsubstituted phenylboronic acid having the structure:
wherein R 4 and R 5 are linked by a spacer, wherein said spacer is the product of a Click chemistry reaction between an azide group of a linker covalently attached to the boronic acid (R 5 ) and a reactive alkynyl group of a tether which has a second alkynyl group conjugated to the base (R 4 ), wherein the first aptamer has enhanced selective affinity for a glycosylated site of the target polypeptide compared to a second aptamer having an identical nucleotide sequence to that of the first aptamer but not having a boronic acid group thereon;
(c) providing conditions suitable for selective binding of the first aptamer to the glycosylated site of the target polypeptide; and
(d) detecting a population of bound first aptamers, thereby indicating the presence of the glycosylation site of the target polypeptide.
22. The method of claim 21 , wherein the glycosylation site of the target polypeptide comprises a region of a glycosylation chain and a region of the polypeptide.
23. The method of claim 21 , wherein R 4 is uracil, R 2 is OH, and R 3 is H.
24. The method of claim 21 , wherein R 5 is a boronic acid selected from the group consisting of: a substituted phenylboronic acid, a naphthalenylboronic acid, a quinolinylboronic acid, a pyridinylboronic acid, a furanylboronic acid, a thiophenylboronic acid, an indolylboronic acid, a 1,8-naphthalimide-based boronic acid, an a α-acetaminoalkylboronic acid, a quinolin-4-ylboronic acid, a quinolin-5-ylboronic acid, a quinolin-8-ylboronic acid, a pyridinylboronic acid, a furan-2-ylboronic acid, and a thiophen-2-ylboronic acid.
25. The method of claim 21 , wherein the boronic acid is a fluorescent boronic acid selected from the group consisting of the structures:
26. The method of claim 21 , wherein the target polypeptide is selected from the group consisting of: an isolated polypeptide or a fragment thereof, a polypeptide in a cell or tissue of an animal or plant, or a cultured cell.
27. The method of claim 21 , wherein the target polypeptide is Prostate Serum Antigen (PSA) or fibrinogen.
28. The method of claim 27 , wherein the first aptamer selectively binds to high pl PSA, low pl PSA, or both high and low pl PSA.
29. The method of claim 27 , wherein the aptamer selectively binds to a glycosylated species of fibrinogen.