Questions about CpG concept

Question

[mangfu100]

Hi all.

I am reading a paper but I couldn't understand some concepts even though I tried to search it on the web.

here is the paper's address and in the article, below bold sentence is what I didn't understand. (http://www.nature.com/nature/journal/v500/n7463/full/nature12477.html)

Both are characterized by prominence of C>T substitutions at NpCpG trinucleotides.

Signature 2 is characterized by C>T and C>G mutations at TpCpN trinucleotides.

I know what the CpG is. (I think that it is a site where C and G frequently appear). However what the Np is?

Also, I didn't get what the TpCpN is.. what is the meaning of N?

I really appreciate it if you could help me understand :)

Answer 1

[kloetzl]

The p is the phosphorus group connecting two nucleotides in the DNA. Thus CpG is a Cytosine followed by a Guanine, on the same strand. N is any nucleotide. So NpCpG is any nucleotide followed by C followed by G. It is written CpG to distinguish it from CG bonding base pairs.