Nucleic acid adaptors and uses thereof

A method for circularizing a polynucleotide, comprising:

• a) providing (i) a linear target polynucleotide having a first end and a second end, (ii) a first double-stranded nucleic acid adaptor with a target joining end and a first overhang end wherein the first overhang end comprises a first overhang nucleic acid sequence, (iii) and a second double-stranded nucleic acid adaptor with a target-joining end and a second overhang end wherein the second overhang end comprises a second overhang nucleic acid sequence, wherein the first and second overhang nucleic acid sequences being at least partially complementary to each other, wherein the first overhang is hybridized to a first single-stranded blocking oligonucleotide over at least a portion of its length and the second overhang is hybridized to a second single-stranded blocking oligonucleotide over at least a portion of its length, and wherein the target-joining end of the first double-stranded nucleic acid adaptor is joined to the first end of the linear target polynucleotide and the target joining end of the second double-stranded nucleic acid adaptor is joined to the second end of the linear target polynucleotide;
• b) removing the first and the second single-stranded blocking oligonucleotides from the first and the second overhangs;
• and
• c) hybridizing the first overhang having a first nucleic acid sequence with the second overhang having a second nucleic acid sequence, thereby circularizing the polynucleotide, wherein the first and second overhangs are not enzymatically ligated together.