Diversity of human endogenous retrovirus class II-like sequences

Class II human endogenous retroviruses (HERVs), often referred to as mouse mammary tumour virus (MMTV)-like or HERV-K elements, have similarities to s everal animal infectious retroviruses, Single clones from each of nine clas s II HERV groups (NMWV 1 to NMWV 9), isolated from a human breast cancer ce ll genomic library, were sequenced over a 244 bp stretch of the conserved r everse transcriptase region. These sequences were aligned to related exogen ous and endogenous retroviruses and a phylogenetic tree was constructed. Se quences with more than 80% identity were considered as members of one group and we report here that the class II HERV family consists of at least ten groups. Three of the sequenced clones, from groups NMWV 3, 7 and 9, could n ot be related to any other previously identified elements and constituted t heir own groups. NMWV 8 had no similarity to any retroviral sequences in th e sequenced region and is so far considered to be non-retroviral.