Pooled adapter strategy for reducing bias in small RNA characterization
Modified nucleic acid adapters are provided that collectively provide a mixture of nucleotides at the 3′ end of 5′ adapters and at the 5′ end of 3′ adapters such that at least one adapter in each set has any given nucleotide at position 1, i.e., the nucleotide position available for ligation to a small RNA, and has any given nucleotide at position 2 adjacent to position 1 for use in overcoming bias during nucleic acid manipulation, such as small RNA characterization and/or profiling by, e.g., deep sequencing, along with methods for use of the modified adapters in small RNA characterization. The modified adapters have at least two mixed nucleotides at the adapter terminus to be ligated to a nucleic acid such as a small RNA.
1. A mixture of 3′ DNA adapters for small RNA characterization comprising:
a plurality of modified adapter sequences that are covalently extended at the 5′ ends by addition of at least two random nucleotides, wherein the modified adapter sequences comprise the structure NNe, wherein e is the adaptor sequence, and wherein NN are at least two random nucleotides that have been covalently attached to the 5′ end of the adapter sequence;
wherein at least one modified adapter sequence further comprises an activated riboadenylation (rAPP) at the 5′ end of the modified adapter sequence, wherein the at least two random nucleotides are internal to the activated riboadenylation (5′rAPP-NNe-3′);
wherein the mixture comprises at least sixteen modified adapter sequences for each unique adapter sequence wherein the at least sixteen modified adapter sequences comprise AAe, ACe, AGe, ATe, CAe, CCe, CGe, CTe, GAe, GCe, GGe, GTe, TAe, TCe, TGe, and TTe; and
wherein A is a deoxyadenylate nucleotide; C is a deoxycytidylate nucleotide; G is a deoxyguanylate nucleotide; and T is a thymidylate nucleotide.
2. The mixture of 3′ DNA adapters according to claim 1 , wherein the 3′ adapters are 3′ RNA adapters.
3. The mixture of 3′ DNA adapters according to claim 1 , wherein at least one modified adapter sequence further comprises a restriction endonuclease cleavage site.
4. The mixture of 3′ DNA adapters according to claim 1 , wherein each adapter sequence of unique sequence is present in about equimolar concentration relative to other adapter sequences of unique sequence in the mixture.
5. The mixture of 3′ DNA adapters according to claim 1 , wherein at least one modified adapter sequence further comprises a PCR primer binding site.
6. The mixture of 3′ DNA adapters according to claim 1 , wherein at least one modified adapter sequence comprises: deoxyinosine; deoxy-5-bromouridylate; or deoxyinosine and deoxy-5-bromouridylate.
7. The mixture of 3′ DNA adapters according to claim 1 , wherein at least one modified adapter sequence further comprises a dideoxy nucleotide at the 3′ end of the modified adapter sequence.
8. The mixture of 3′ DNA adapters according to claim 1 , wherein at least one 3′ adapter comprises ribonucleotides.
9. The mixture of 3′ DNA adapters according to claim 1 , wherein at least one modified adapter sequence further comprises a restriction endonuclease cleavage site.
10. The mixture of 3′ DNA adapters according to claim 1 , wherein at least one modified adapter sequence further comprises a PCR primer binding site.
11. The mixture of 3′ DNA adapters of claim 7 , wherein the dideoxy nucleotide is ddC.
12. The mixture of 3′ DNA adapters according to claim 1 , wherein: at least one modified adapter sequence AAe comprises AAAe, AACe, AAGe, or AATe; at least one modified adapter sequence ACe comprises ACAe, ACCe, ACGe, or ACTe; at least one modified adapter sequence AGe comprises AGAe, AGCe, AGGe, or AGTe; at least one modified adapter sequence ATe, comprises ATAe, ATCe, ATGe, or ATTe; at least one modified adapter sequence CAe comprises CAAe, CACe, CAGe, or CATe; at least one modified adapter sequence CCe comprises CCAe, CCCe, CCGe, or CCTe; at least one modified adapter sequence CGe comprises CGAe, CGCe, CGGe, or CGTe; at least one modified adapter sequence CTe comprises CTAe, CTCe, CTGe, or CTTe; at least one modified adapter sequence GAe comprises GAAe, GACe, GAGe, or GATe; at least one modified adapter sequence GCe comprises GCAe, GCCe, GCGe, or GCTe; at least one modified adapter sequence GGe comprises GGAe, GGCe, GGGe, or GGTe; at least one-modified adapter sequence GTe comprises GTAe, GTCe, GTGe, or GTTe; at least one modified adapter sequence TAe comprises TAAe, TACe, TAGe, or TATe; at least one modified adapter sequence TCe comprises TCAe, TCTe, TCGe, or TCTe; at least one modified adapter sequence TGe comprises TGAe, TGCe, TGGe, or TGTe; or at least one modified adapter sequence TTe comprises TTAe, TTCe, TTGe, or TTTe.
13. The mixture of adapters according to claim 12 , wherein the random nucleotides of at least one modified adapter sequence further comprises an additional A, C, G, or T random nucleotide.
14. A mixture of 5′ adapters and 3′ adapters comprising:
a plurality of 5′ modified adapter sequences and a plurality of 3′ modified adapter sequences, wherein the 5′ modified adapter sequences comprise RNA and the 3′ modified adapter sequences comprise DNA and an activated riboadenylation (rAPP) at the 5′ end;
wherein each modified adapter sequence comprises an adapter sequence and two random nucleotides, wherein the two random nucleotides are located on the 3′ end of the 5′ modified adapter sequences and wherein the two random nucleotides are located between the activated adenylation and the adapter sequence of the 3′ modified adapter sequences;
wherein for each 5′ adapter sequence of unique sequence in the mixture, the mixture comprises sixteen modified adapter sequences, each comprising the unique adapter sequence and one of the sixteen possible combinations of two random nucleotides; and
wherein for each 3′ adapter sequence of unique sequence in the mixture, the mixture comprises sixteen modified adapter sequences, each comprising the unique adapter sequence and one of the sixteen possible combinations of two random nucleotides.
15. A mixture of 5′ adapters and 3′ adapters comprising:
a plurality of 5′ modified adapter sequences and a plurality of 3′ modified adapter sequences, wherein the 5′ modified adapter sequences comprise RNA and the 3′ modified adapter sequences comprise DNA and an activated riboadenylation (rAPP) at the 5′ end;
wherein each modified adapter sequence comprises an adapter sequence and three random nucleotides, wherein the three random nucleotides are located on the 3′ end of the 5′ modified adapter sequences and wherein the three random nucleotides are located between the activated adenylation and the adapter sequence of the 3′ modified adapter sequences;
wherein for each 5′ adapter sequence of unique sequence in the mixture, the mixture comprises sixty four modified adapter sequences, each comprising the unique adapter sequence and one of the sixty four possible combinations of three random nucleotides; and
wherein for each 3′ adapter sequence of unique sequence in the mixture, the mixture comprises sixty four modified adapter sequences, each comprising the unique adapter sequence and one of the sixty four possible combinations of three random nucleotides.
16. A mixture of 5′ adapters and 3′ adapters comprising:
a plurality of 5′ modified adapter sequences and a plurality of 3′ modified adapter sequences, wherein the 5′ modified adapter sequences comprise RNA and the 3′ modified adapter sequences comprise DNA and an activated riboadenylation (rAPP) at the 5′ end;
wherein each modified adapter sequence comprises an adapter sequence and four random nucleotides, wherein the four random nucleotides are located on the 3′ end of the 5′ modified adapter sequences and wherein the four random nucleotides are located between the activated adenylation and the adapter sequence of the 3′ modified adapter sequences;
wherein for each 5′ adapter sequence of unique sequence in the mixture, the mixture comprises two hundred and fifty six modified adapter sequences, each comprising the unique adapter sequence and one of the two hundred and fifty six possible combinations of four random nucleotides; and
wherein for each 3′ adapter sequence of unique sequence in the mixture, the mixture comprises two hundred and fifty six modified adapter sequences, each comprising the unique adapter sequence and one of the two hundred and fifty six possible combinations of four random nucleotides.
17. The mixture of 3′ DNA adapters according to claim 1 , wherein the at least two random nucleotides comprise deoxyguanylate, deoxyadenylate, thymidylate, deoxycytidylate, guanylate, adenylate, uridylate, cytidylate, deoxyinosine monophosphate, inosine monophosphate, deoxy-5-bromouridylate or 5-bromouridylate.