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 :)