Compositions and methods for analyzing modified nucleotides
Methods and compositions are provided for identifying any of the presence, location and phasing of methylated and/or hydroxymethylated cytosines in nucleic acids including long stretches of DNA. In some embodiments, the method may comprise reacting a first portion (aliquot) of a nucleic acid sample with a dioxygenase and optionally a glucosyltransferase in a reaction mixture containing the nucleic acid followed by a reaction with a cytidine deaminase to detect and optionally map 5m C in a DNA. Optionally, a second portion can be reacted with glucosyltransferase followed by reaction with a cytidine deaminase to detect and optionally map 5hm C in a DNA.
1 . A method comprising:
(a) reacting a nucleic acid sample with a methylcytosine dioxygenase and a glucosyltransferase in a single reaction;
(b) reacting at least some of the product of step (a) with a cytidine deaminase; and
(c) determining the methylation status of a sequence in the nucleic acid sample by sequencing the reaction product of step (b) to determine which cytosine nucleotides have been converted to uracil.
2 . The method according to claim 1 , wherein the methylcytosine dioxygenase has an amino acid sequence that is at least 90% identical to SEQ ID NO:1.
3 . The method of claim 1 , wherein the methylcytosine dioxygenase has an amino acid sequence that is at least 90% identical to SEQ ID NO:3.
4 . The method of claim 1 , wherein, prior to step (b) after reaction with the methylcytosine dioxygenase and the glycosyltransferase, the nucleic acid is purified.
5 . The method of claim 1 , wherein, prior to step (b) after reaction with the methylcytosine dioxygenase and the glycosyltransferase, the nucleic acid is not purified.
6 . The method of claim 1 , wherein in step (b), the reaction is performed on an aliquot of the product of step (a).
7 . The method of claim 1 , wherein the nucleic acid sample of (a) is an aliquot of a nucleic acid sample.
8 . The method of claim 7 , further comprising:
(d) reacting a second aliquot of the nucleic acid sample with a glucosyltransferase in the absence of a methylcytosine dioxygenase;
(e) reacting at least some of the product of step (d) with a cytidine deaminase; and
(f) determining the methylation status of a sequence in the nucleic acid sample by sequencing the reaction product of step (e) to determine which cytosine nucleotides have been converted to uracil, wherein hydroxymethyl cytosines are thereby distinguished from cytosines and methyl cytosines.
9 . The method of claim 1 , wherein the cytidine deaminase is an APOBEC family cytidine deaminase.