Modified nucleic acid molecules and uses thereof

A polynucleotide, wherein at least one base is 1,6-Dimethyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-(1-propynyl)-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-(2-propynyl)-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-allyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-ethynyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-homoallyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-vinyl-pseudo-uracil, 1-Methyl-6-(2,2,2-Trifluoroethyl)pseudo-uracil, 1-Methyl-6-(4-morpholino)-pseudo-uracil, 1-Methyl-6-(4-thiomorpholino)-pseudo-uracil, 1-Methyl-6-(optionally substituted phenyl)pseudo-uracil, 1-Methyl-6-amino-pseudo-uracil, 1-Methyl-6-azido-pseudo-uracil, 1-Methyl-6-bromo-pseudo-uracil, 1-Methyl-6-butyl-pseudo-uracil, 1-Methyl-6-chloro-pseudo-uracil, 1-Methyl-6-cyano-pseudo-uracil, 1-Methyl-6-dimethylamino-pseudo-uracil, 1-Methyl-6-ethoxy-pseudo-uracil, 1-Methyl-6-ethylcarboxylate-pseudo-uracil, 1-Methyl-6-ethyl-pseudo-uracil, 1-Methyl-6-fluoro-pseudo-uracil, 1-Methyl-6-formyl-pseudo-uracil, 1-Methyl-6-hydroxyamino-pseudo-uracil, 1-Methyl-6-hydroxy-pseudo-uracil, 1-Methyl-6-iodo-pseudo-uracil, 1-Methyl-6-iso-propyl-pseudo-uracil, 1-Methyl-6-methoxy-pseudo-uracil, 1-Methyl-6-methylamino-pseudo-uracil, 1-Methyl-6-phenyl-pseudo-uracil, 1-Methyl-6-propyl-pseudo-uracil, 1-Methyl-6-tert-butyl-pseudo-uracil, 1-Methyl-6-trifluoromethoxy-pseudo-uracil, 1-Methyl-6-trifluoromethyl-pseudo-uracil, 6-(2,2,2-Trifluoroethyl)-pseudo-uracil, 6-(4-Morpholino)-pseudo-uracil, 6-(4-Thiomorpholino)-pseudo-uracil, 6-(optionally substituted-Phenyl)-pseudo-uracil, 6-Amino-pseudo-uracil, 6-Azido-pseudo-uracil, 6-Bromo-pseudo-uracil, 6-Butyl-pseudo-uracil, 6-Chloro-pseudo-uracil, 6-Cyano-pseudo-uracil, 6-Dimethylamino-pseudo-uracil, 6-Ethoxy-pseudo-uracil, 6-Ethylcarboxylate-pseudo-uracil, 6-Ethyl-pseudo-uracil, 6-Fluoro-pseudo-uracil, 6-Formyl-pseudo-uracil, 6-Hydroxyamino-pseudo-uracil, 6-Hydroxy-pseudo-uracil, 6-Iodo-pseudo-uracil, 6-iso-Propyl-pseudo-uracil, 6-Methoxy-pseudo-uracil, 6-Methylamino-pseudo-uracil, 6-Methyl-pseudo-uracil, 6-Phenyl-pseudo-uracil, 6-Propyl-pseudo-uracil, 6-tert-Butyl-pseudo-uracil, 6-Trifluoromethoxy-pseudo-uracil, 6-Trifluoromethyl-pseudo-uracil, 1-(3-Amino-3-carboxypropyl)pseudo-uracil, 1-(2,2,2-Trifluoroethyl)-pseudo-uracil, 1-(2,4,6-Trimethyl-benzyl)pseudo-uracil, 1-(2,4,6-Trimethyl-phenyl)pseudo-uracil, 1-(2-Amino-2-carboxyethyl)pseudo-uracil, 1-(2-Amino-ethyl)pseudo-uracil, 1-(3-Amino-propyl)pseudo-uracil, 1-(4-Amino-4-carboxybutyl)pseudo-uracil, 1-(4-Amino-benzyl)pseudo-uracil, 1-(4-Amino-butyl)pseudo-uracil, 1-(4-Amino-phenyl)pseudo-uracil, 1-(4-Methoxy-benzyl)pseudo-uracil, 1-(4-Methoxy-phenyl)pseudo-uracil, 1-(4-Methyl-benzyl)pseudo-uracil, 1-(4-Nitro-benzyl)pseudo-uracil, 1-(4-Nitro-phenyl)pseudo-uracil, 1-(5-Amino-pentyl)pseudo-uracil, 1-(6-Amino-hexyl)pseudo-uracil, 1-Aminomethyl-pseudo-uracil, 1-Benzyl-pseudo-uracil, 1-Butyl-pseudo-uracil, 1-Cyclobutylmethyl-pseudo-uracil, 1-Cyclobutyl-pseudo-uracil, 1-Cycloheptylmethyl-pseudo-uracil, 1-Cycloheptyl-pseudo-uracil, 1-Cyclohexylmethyl-pseudo-uracil, 1-Cyclohexyl-pseudo-uracil, 1-Cyclooctylmethyl-pseudo-uracil, 1-Cyclooctyl-pseudo-uracil, 1-Cyclopentylmethyl-pseudo-uracil, 1-Cyclopentyl-pseudo-uracil, 1-Cyclopropylmethyl-pseudo-uracil, 1-Cyclopropyl-pseudo-uracil, 1-Ethyl-pseudo-uracil, 1-Hexyl-pseudo-uracil, 1-iso-Propyl-pseudo-uracil 1-Pentyl-pseudo-uracil, 1-Phenyl-pseudo-uracil, 1-Propyl-pseudo-uracil, 1-p-toluyl-pseudo-uracil, 1-tert-Butyl-pseudo-uracil, 1-Trifluoromethyl-pseudo-uracil, 3-(optionally substituted C1-C6 Alkyl)-pseudo-uracil, Pseudo-uracil-N1-2-ethanoic acid, Pseudo-uracil-N1-3-propionic acid, Pseudo-uracil-N1-4-butanoic acid, Pseudo-uracil-N1-5-pentanoic acid, Pseudo-uracil-N1-6-hexanoic acid, Pseudo-uracil-N1-7-heptanoic acid, Pseudo-uracil-N1-methyl-p-benzoic acid, 6-phenyl-pseudo-uracil, 6-azido-pseudo-uracil, Pseudo-uracil-N1-p-benzoic acid, N3-Methyl-pseudo-uracil, 5-Methyl-amino-methyl-uracil, 5-Carboxy-methyl-amino-methyl-uracil, 5-(carboxyhydroxymethyl)uracil methyl ester 5-(carboxyhydroxymethyl)uracil, 2-anhydro-cytosine, 2-anhydro-uracil, 5-Methoxycarbonylmethyl-2-thio-uracil, 5-Methylaminomethyl-2-seleno-uracil, 5-(iso-Pentenylaminomethyl)-uracil, 5-(iso-Pentenylaminomethyl)-2-thio-uracil, 5-(iso-Pentenylaminomethyl)-uracil, 5-Trideuteromethyl-6-deutero-uracil, 5-(2-Chloro-phenyl)-2-thio-cytosine, 5-(4-Amino-phenyl)-2-thio-cytosine, 5-(2-Furanyl)-uracil, 8-Trifluoromethyl-adenine, 2-Trifluoromethyl-adenine, 3-Deaza-3-fluoro-adenine, 3-Deaza-3-bromo-adenine, 3-Deaza-3-iodo-adenine, 1-Hydroxymethyl-pseudo-uracil, 1-(2-Hydroxyethyl)-pseudo-uracil, 1-Methoxymethyl-pseudo-uracil, 1-(2-Methoxyethyl)-pseudo-uracil, 1-(2,2-Diethoxyethyl)-pseudo-uracil, 1-(2-Hydroxypropyl)-pseudo-uracil, (2R)-1-(2-Hydroxypropyl)-pseudo-uracil, (2S)-1-(2-Hydroxypropyl)-pseudo-uracil, 1-Cyanomethyl-pseudo-uracil, 1-Morpholinomethyl-pseudo-uracil, 1-Thiomorpholinomethyl-pseudo-uracil, 1-Benzyloxymethyl-pseudo-uracil, 1-(2,2,3,3,3-Pentafluoropropyl)-pseudo-uracil, 1-Thiomethoxymethyl-pseudo-uracil, 1-Methanesulfonylmethyl-pseudo-uracil, 1-Vinyl-pseudo-uracil, 1-Allyl-pseudo-uracil, 1-Homoallyl-pseudo-uracil, 1-Propargyl-pseudo-uracil, 1-(4-Fluorobenzyl)-pseudo-uracil, 1-(4-Chlorobenzyl)-pseudo-uracil, 1-(4-Bromobenzyl)-pseudo-uracil, 1-(4-Iodobenzyl)-pseudo-uracil, 1-(4-Methylbenzyl)-pseudo-uracil, 1-(4-Trifluoromethylbenzyl)-pseudo-uracil, 1-(4-Methoxybenzyl)-pseudo-uracil, 1-(4-Trifluoromethoxybenzyl)-pseudo-uracil, 1-(4-Thiomethoxybenzyl)-pseudo-uracil, 1-(4-Methanesulfonylbenzyl)-pseudo-uracil, Pseudo-uracil 1-(4-methylbenzoic acid), Pseudo-uracil 1-(4-methylbenzenesulfonic acid), 1-(2,4,6-Trimethylbenzyl)-pseudo-uracil, 1-(4-Nitrobenzyl)-pseudo-uracil, 1-(4-Azidobenzyl)-pseudo-uracil, 1-(3,4-Dimethoxybenzyl)-pseudo-uracil, 1-(3,4-Bis-trifluoromethoxybenzyl)-pseudo-uracil, 1-Acetyl-pseudo-uracil, 1-Trifluoroacetyl-pseudo-uracil, 1-Benzoyl-pseudo-uracil, 1-Pivaloyl-pseudo-uracil, 1-(3-Cyclopropyl-prop-2-ynyl)-pseudo-uracil, Pseudo-uracil 1-methylphosphonic acid diethyl ester, Pseudo-uracil 1-methylphosphonic acid, Pseudo-uracil 1-[3-(2-ethoxy)]propionic acid, Pseudo-uracil 1-[3-{2-(2-ethoxy)-ethoxy}]propionic acid, Pseudo-uracil 1-[3-{2-(2-[2-ethoxy]-ethoxy)-ethoxy}]propionic acid, Pseudo-uracil 1-[3-{2-(2-[2-(2-ethoxy)-ethoxy]-ethoxy)-ethoxy}]propionic acid, Pseudo-uracil 1-[3-{2-(2-[2-{2-(2-ethoxy)-ethoxy}-ethoxy]-ethoxy)-ethoxy}]propionic acid, 1-{3-[2-(2-Aminoethoxy)-ethoxy]-propionyl}pseudo-uracil, 1-[3-(2-{2-[2-(2-Aminoethoxy)-ethoxy]-ethoxy}-ethoxy)-propionyl]-pseudo-uracil, 1-Biotinyl-pseudo-uracil, 1-Biotinyl-PEG2-pseudo-uracil, 5-(C3-8 cycloalkyl)-cytosine, 5-methyl-N6-acetyl-cytosine, 5-(carboxymethyl)-N6-trifluoroacetyl-cytosine trifluoromethyl ester, N6-propionyl-cytosine, 5-monofluoromethyl-cytosine, 5-trifluoromethoxy-cytosine, N6-(1,1,1-trifluoro-propionyl)-cytosine, 4-acetyl-pseudo-isocytosine, 1-ethyl-pseudo-isocytosine, 1-hydroxy-pseudo-isocytosine, or 1-(2,2,2-trifluoroethyl)-pseudo-uracil.

An isolated polynucleotide encoding a polypeptide of interest, said isolated polynucleotide comprising:

• (a) a 5′ UTR comprising at least one Kozak sequence;
• (b) a 3′ UTR;
• and
• (c) at least one 5′ cap structure,
• wherein at least one base is 1-Methyl-3-(3-amino-3-carboxypropyl)pseudo-uracil, 5-Oxyacetic acid-methyl ester-uracil, 5-Trifluoromethyl-cytidine, 5-Trifluoromethyl-uracil, 5-Carboxymethylaminomethyl-2-thio-uracil, 5-Methylaminomethyl-2-thio-uracil, 5-Methoxy-carbonyl-methyl-uracil, 5-Oxyacetic acid-uracil, 3-(3-Amino-3-carboxypropyl)-uracil, 2-Amino-adenine, 8-Aza-adenine, Xanthosine, 5-Bromo-cytosine, 5-Aminoallyl-cytosine, 5-iodo-cytosine, 8-bromo-adenine, 8-bromo-guanine, N4-Benzoyl-cytosine, N4-Amino-cytosine, N6-Bz-adenine, N2-isobutyl-guanine, 5-Methylaminomethyl-2-thio-uracil, 5-Carbamoylmethyl-uracil, 1-Methyl-3-(3-amino-3-carboxypropyl) pseudo-uracil, 5-Methyldihydro-uracil, 5-(1-propynyl)cytosine, 5-Ethynylcytosine, 5-vinyl-uracil, (Z)-5-(2-Bromo-vinyl)-uracil, (E)-5-(2-Bromo-vinyl)-uracil, 5-Methoxy-cytosine, 5-Formyl-uracil, 5-Cyano-uracil, 5-Dimethylamino-uracil, 5-Cyano-cytosine, 5-Phenylethynyl-uracil, (E)-5-(2-Bromo-vinyl)-cytosine, 2-Mercapto-adenine, 2-Azido-adenine, 2-Fluoro-adenine, 2-Chloro-adenine, 2-Bromo-adenine, 2-Iodo-adenine, 7-Amino-1H-pyrazolo[4,3-d]pyrimidine, 2,4-dihydropyrazolo[4,3-d]pyrimidin-7-one, 2,4-dihydropyrazolo[4,3-d]pyrimidine-5,7-dione, pyrrolosine, 9-Deaza-adenine, 9-Deaza-guanine, 3-Deaza-adenine, 3-Deaza-3-chloro-adenine, 1-Deaza-adenine, 5-vinyl-cytosine, 5-phenyl-cytosine, 5-difluoromethyl-cytosine, 5-(1-propynyl)-uracil, 5-(1-propynyl)-cytosine, or 5-methoxymethyl-cytosine.

A compound of Formula I:

• A-B, Formula I
• wherein A is:
• wherein the dashed line represents an optional double bond;
• each of U and U′ is, independently, O, S, N(RU)nu, or C(RU)nu, wherein nu is an integer from 0 to 2 and each RU is, independently, H, halo, or optionally substituted C1-C6 alkyl;
• each of R1′, R2′, R1″, R2″, R1, R2, R3′, R4, R5, R6, and R7 is, independently, H, halo, hydroxy, thiol, optionally substituted C1-C6 alkyl, optionally substituted C1-C6 alkynyl, optionally substituted C1-C6 heteroalkyl, optionally substituted C2-C6 heteroalkenyl, optionally substituted C2-C6 heteroalkynyl, optionally substituted amino, azido, optionally substituted C6-C10 aryl;
• or R5 can join together with one or more of R1′, R1″, R2′, or R2″ to form optionally substituted C1-C6 alkylene or optionally substituted C1-C6 heteroalkylene and, taken together with the carbons to which they are attached, provide an optionally substituted C2-C9 heterocyclyl;
• or R4 can join together with one or more of R1′, R1″, R2′, R2″, R3, or R5 to form optionally substituted C1-C6 alkylene or optionally substituted C1-C6 heteroalkylene and, taken together with the carbons to which they are attached, provide an optionally substituted C2-C9 heterocyclyl;
• R3 is H, halo, hydroxy, thiol, optionally substituted C1-C6 alkyl, optionally substituted C1-C6alkynyl, optionally substituted C1-C6 heteroalkyl, optionally substituted C2-C6 heteroalkenyl, optionally substituted C2-C6 heteroalkynyl, optionally substituted amino, azido, optionally substituted C6-C10 aryl;
• or R3 can join together with one or more of R1′, R1″, R2′, R2″, and, taken together with the carbons to which they are attached, provide an optionally substituted C2-C9 heterocyclyl;
• wherein if said optional double bond is present, R3 is absent;
• each of m′ and m″ is, independently, an integer from 0 to 3;
• each of q and r is independently, an integer from 0 to 5;
• each of Y1, Y2, and Y3, is, independently, hydrogen, O, S, Se, —NRN1—, optionally substituted C1-C6 alkylene, or optionally substituted C1-C6 heteroalkylene, wherein RN1 is H, optionally substituted C1-C6 alkyl, optionally substituted C2-C6 alkenyl, optionally substituted C2-C6 alkynyl, optionally substituted C6-C10 aryl, or absent;
• each of Y4 and Y6 is, independently, H, hydroxyl, protected hydroxyl, halo, thiol, boranyl, optionally substituted C1-C6 alkyl, optionally substituted C2-C6 alkenyl, optionally substituted C2-C6 alkynyl, optionally substituted C1-C6 heteroalkyl, optionally substituted C2-C6 heteroalkenyl, optionally substituted C2-C6 heteroalkynyl, optionally substituted amino, or absent;
• Y5 is O, S, Se, optionally substituted C1-C6 alkylene, or optionally substituted C1-C6 heteroalkylene;
• and
• B is 1,6-Dimethyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-(1-propynyl)-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-(2-propynyl)-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-allyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-ethynyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-homoallyl-pseudo-uracil, 1-(optionally substituted C1-C6 Alkyl)-6-vinyl-pseudo-uracil, 1-Methyl-6-(2,2,2-Trifluoroethyl)pseudo-uracil, 1-Methyl-6-(4-morpholino)-pseudo-uracil, 1-Methyl-6-(4-thiomorpholino)-pseudo-uracil, 1-Methyl-6-(optionally substituted phenyl)pseudo-uracil, 1-Methyl-6-amino-pseudo-uracil, 1-Methyl-6-azido-pseudo-uracil, 1-Methyl-6-bromo-pseudo-uracil, 1-Methyl-6-butyl-pseudo-uracil, 1-Methyl-6-chloro-pseudo-uracil, 1-Methyl-6-cyano-pseudo-uracil, 1-Methyl-6-dimethylamino-pseudo-uracil, 1-Methyl-6-ethoxy-pseudo-uracil, 1-Methyl-6-ethylcarboxylate-pseudo-uracil, 1-Methyl-6-ethyl-pseudo-uracil, 1-Methyl-6-fluoro-pseudo-uracil, 1-Methyl-6-formyl-pseudo-uracil, 1-Methyl-6-hydroxyamino-pseudo-uracil, 1-Methyl-6-hydroxy-pseudo-uracil, 1-Methyl-6-iodo-pseudo-uracil, 1-Methyl-6-iso-propyl-pseudo-uracil, 1-Methyl-6-methoxy-pseudo-uracil, 1-Methyl-6-methylamino-pseudo-uracil, 1-Methyl-6-phenyl-pseudo-uracil, 1-Methyl-6-propyl-pseudo-uracil, 1-Methyl-6-tert-butyl-pseudo-uracil, 1-Methyl-6-trifluoromethoxy-pseudo-uracil, 1-Methyl-6-trifluoromethyl-pseudo-uracil, 6-(2,2,2-Trifluoroethyl)-pseudo-uracil, 6-(4-Morpholino)-pseudo-uracil, 6-(4-Thiomorpholino)-pseudo-uracil, 6-(optionally substituted-Phenyl)-pseudo-uracil, 6-Amino-pseudo-uracil, 6-Azido-pseudo-uracil, 6-Bromo-pseudo-uracil, 6-Butyl-pseudo-uracil, 6-Chloro-pseudo-uracil, 6-Cyano-pseudo-uracil, 6-Dimethylamino-pseudo-uracil, 6-Ethoxy-pseudo-uracil, 6-Ethylcarboxylate-pseudo-uracil, 6-Ethyl-pseudo-uracil, 6-Fluoro-pseudo-uracil, 6-Formyl-pseudo-uracil, 6-Hydroxyamino-pseudo-uracil, 6-Hydroxy-pseudo-uracil, 6-Iodo-pseudo-uracil, 6-iso-Propyl-pseudo-uracil, 6-Methoxy-pseudo-uracil, 6-Methylamino-pseudo-uracil, 6-Methyl-pseudo-uracil, 6-Phenyl-pseudo-uracil, 6-Propyl-pseudo-uracil, 6-tert-Butyl-pseudo-uracil, 6-Trifluoromethoxy-pseudo-uracil, 6-Trifluoromethyl-pseudo-uracil, 1-(3-Amino-3-carboxypropyl)pseudo-uracil, 1-(2,2,2-Trifluoroethyl)-pseudo-uracil, 1-(2,4,6-Trimethyl-benzyl)pseudo-uracil, 1-(2,4,6-Trimethyl-phenyl)pseudo-uracil, 1-(2-Amino-2-carboxyethyl)pseudo-uracil, 1-(2-Amino-ethyl)pseudo-uracil, 1-(3-Amino-propyl)pseudo-uracil, 1-(4-Amino-4-carboxybutyl)pseudo-uracil, 1-(4-Amino-benzyl)pseudo-uracil, 1-(4-Amino-butyl)pseudo-uracil, 1-(4-Amino-phenyl)pseudo-uracil, 1-(4-Methoxy-benzyl)pseudo-uracil, 1-(4-Methoxy-phenyl)pseudo-uracil, 1-(4-Methyl-benzyl)pseudo-uracil, 1-(4-Nitro-benzyl)pseudo-uracil, 1-(4-Nitro-phenyl)pseudo-uracil, 1-(5-Amino-pentyl)pseudo-uracil, 1-(6-Amino-hexyl)pseudo-uracil, 1-Aminomethyl-pseudo-uracil, 1-Benzyl-pseudo-uracil, 1-Butyl-pseudo-uracil, 1-Cyclobutylmethyl-pseudo-uracil, 1-Cyclobutyl-pseudo-uracil, 1-Cycloheptylmethyl-pseudo-uracil, 1-Cycloheptyl-pseudo-uracil, 1-Cyclohexylmethyl-pseudo-uracil, 1-Cyclohexyl-pseudo-uracil, 1-Cyclooctylmethyl-pseudo-uracil, 1-Cyclooctyl-pseudo-uracil, 1-Cyclopentylmethyl-pseudo-uracil, 1-Cyclopentyl-pseudo-uracil, 1-Cyclopropylmethyl-pseudo-uracil, 1-Cyclopropyl-pseudo-uracil, 1-Ethyl-pseudo-uracil, 1-Hexyl-pseudo-uracil, 1-iso-Propyl-pseudo-uracil 1-Pentyl-pseudo-uracil, 1-Phenyl-pseudo-uracil, 1-Propyl-pseudo-uracil, 1-p-toluyl-pseudo-uracil, 1-tert-Butyl-pseudo-uracil, 1-Trifluoromethyl-pseudo-uracil, 3-(optionally substituted C1-C6 Alkyl)-pseudo-uracil, Pseudo-uracil-N1-2-ethanoic acid, Pseudo-uracil-N1-3-propionic acid, Pseudo-uracil-N1-4-butanoic acid, Pseudo-uracil-N1-5-pentanoic acid, Pseudo-uracil-N1-6-hexanoic acid, Pseudo-uracil-N1-7-heptanoic acid, Pseudo-uracil-N1-methyl-p-benzoic acid, 6-phenyl-pseudo-uracil, 6-azido-pseudo-uracil, Pseudo-uracil-N1-p-benzoic acid, N3-Methyl-pseudo-uracil, 5-Methyl-amino-methyl-uracil, 5-Carboxy-methyl-amino-methyl-uracil, 5-(carboxyhydroxymethyl)uracil methyl ester 5-(carboxyhydroxymethyl)uracil, 2-anhydro-cytosine, 2-anhydro-uracil, 5-Methoxycarbonylmethyl-2-thio-uracil, 5-Methylaminomethyl-2-seleno-uracil, 5-(iso-Pentenylaminomethyl)-uracil, 5-(iso-Pentenylaminomethyl)-2-thio-uracil, 5-(iso-Pentenylaminomethyl)-uracil, 5-Trideuteromethyl-6-deutero-uracil, 5-(2-Chloro-phenyl)-2-thio-cytosine, 5-(4-Amino-phenyl)-2-thio-cytosine, 5-(2-Furanyl)-uracil, 8-Trifluoromethyl-adenine, 2-Trifluoromethyl-adenine, 3-Deaza-3-fluoro-adenine, 3-Deaza-3-bromo-adenine, 3-Deaza-3-iodo-adenine, 1-Hydroxymethyl-pseudo-uracil, 1-(2-Hydroxyethyl)-pseudo-uracil, 1-Methoxymethyl-pseudo-uracil, 1-(2-Methoxyethyl)-pseudo-uracil, 1-(2,2-Diethoxyethyl)-pseudo-uracil, 1-(2-Hydroxypropyl)-pseudo-uracil, (2R)-1-(2-Hydroxypropyl)-pseudo-uracil, (2S)-1-(2-Hydroxypropyl)-pseudo-uracil, 1-Cyanomethyl-pseudo-uracil, 1-Morpholinomethyl-pseudo-uracil, 1-Thiomorpholinomethyl-pseudo-uracil, 1-Benzyloxymethyl-pseudo-uracil, 1-(2,2,3,3,3-Pentafluoropropyl)-pseudo-uracil, 1-Thiomethoxymethyl-pseudo-uracil, 1-Methanesulfonylmethyl-pseudo-uracil, 1-Vinyl-pseudo-uracil, 1-Allyl-pseudo-uracil, 1-Homoallyl-pseudo-uracil, 1-Propargyl-pseudo-uracil, 1-(4-Fluorobenzyl)-pseudo-uracil, 1-(4-Chlorobenzyl)-pseudo-uracil, 1-(4-Bromobenzyl)-pseudo-uracil, 1-(4-Iodobenzyl)-pseudo-uracil, 1-(4-Methylbenzyl)-pseudo-uracil, 1-(4-Trifluoromethylbenzyl)-pseudo-uracil, 1-(4-Methoxybenzyl)-pseudo-uracil, 1-(4-Trifluoromethoxybenzyl)-pseudo-uracil, 1-(4-Thiomethoxybenzyl)-pseudo-uracil, 1-(4-Methanesulfonylbenzyl)-pseudo-uracil, Pseudo-uracil 1-(4-methylbenzoic acid), Pseudo-uracil 1-(4-methylbenzenesulfonic acid), 1-(2,4,6-Trimethylbenzyl)-pseudo-uracil, 1-(4-Nitrobenzyl)-pseudo-uracil, 1-(4-Azidobenzyl)-pseudo-uracil, 1-(3,4-Dimethoxybenzyl)-pseudo-uracil, 1-(3,4-Bis-trifluoromethoxybenzyl)-pseudo-uracil, 1-Acetyl-pseudo-uracil, 1-Trifluoroacetyl-pseudo-uracil, 1-Benzoyl-pseudo-uracil, 1-Pivaloyl-pseudo-uracil, 1-(3-Cyclopropyl-prop-2-ynyl)-pseudo-uracil, Pseudo-uracil 1-methylphosphonic acid diethyl ester, Pseudo-uracil 1-methylphosphonic acid, Pseudo-uracil 1-[3-(2-ethoxy)]propionic acid, Pseudo-uracil 1-[3-{2-(2-ethoxy)-ethoxy}]propionic acid, Pseudo-uracil 1-[3-{2-(2-[2-ethoxy]-ethoxy)-ethoxy}]propionic acid, Pseudo-uracil 1-[3-{2-(2-[2-(2-ethoxy)-ethoxy]-ethoxy)-ethoxy}]propionic acid, Pseudo-uracil 1-[3-{2-(2-[2-{2-(2-ethoxy)-ethoxy}-ethoxy]-ethoxy)-ethoxy}]propionic acid, 1-{3-[2-(2-Aminoethoxy)-ethoxy]-propionyl}pseudo-uracil, 1-[3-(2-{2-[2-(2-Aminoethoxy)-ethoxy]-ethoxy}-ethoxy)-propionyl]-pseudo-uracil, 1-Biotinyl-pseudo-uracil, 1-Biotinyl-PEG2-pseudo-uracil, 5-cyclopropyl-cytosine, 5-methyl-N6-acetyl-cytosine, 5-(carboxymethyl)-N6-trifluoroacetyl-cytosine trifluoromethyl ester, N6-propionyl-cytosine, 5-monofluoromethyl-cytosine, 5-trifluoromethoxy-cytosine, N6-(1,1,1-trifluoro-propionyl)-cytosine, 4-acetyl-pseudo-isocytosine, 1-ethyl-pseudo-isocytosine, 1-hydroxy-pseudo-isocytosine, or 1-(2,2,2-trifluoroethyl)-pseudo-uracil;
• or a salt thereof.