This family also contains the NS2 protein. Parvoviruses encode two non-structural proteins, NS1 and NS2. The mRNA for NS2 contains the coding sequence for the first 87 amino acids of NS1, then by an alternative splicing mechanism mRNA from a different reading frame, encoding the last 78 amino acids, makes up the full length of the NS2 mRNA. NS1, is the major non-structural protein. It is essential for DNA replication. It is an 83-kDa nuclear phosphoprotein. It has DNA helicase and ATPase activity.