The MHC class I heavy chain is a common target of the small proteins encoded by the 3 ' end of HTLV type 1 and HTLV type 2

Human T cell leukemia/lymphotropic virus types 1 and 2 are two immunologica lly and phylogenetically related retroviruses that differ in their pathogen icity in vivo. The overall genetic structure of HTLV-1 and -2 is similar. E ach contains a unique region at the 3' end of the genome, designated the pX region, p12(I) is a membrane-associated protein encoded by the open readin g frame I (ORF I) region of HTLV-1, which lies within the pX region. A corr esponding protein, p10(I) is encoded by the ORF I region of HTLV-2 and an a dditional protein, p11(v), is encoded by ORF V, which overlaps the HTLV-2 O RF I region. As with HTLV-1, the small proteins encoded by the pX region of HTLV-2 appear to be dispensable for viral replication and cellular transfo rmation in vitro. However, the small open reading frames of both viruses ar e important for viral replication irt vivo, which suggests they may play an important role during the viral life cycle. This study was undertaken to i nvestigate and compare the cellular targets of the p10(I), p11(v), and p12( I) putative proteins.