Three protein isoforms are encoded by the human T-cell leukemia/lymphotropic virus type I pX region open reading frames (ORF) I and II through alternative splicing. Both the singly and doubly spliced mRNAs from ORF I encode a single 12-kDa protein (p12(I)), whereas two distinct proteins of 13 kDa (p13(II)) and 30 kDa (p30(II)) are encoded from the ORF II alternatively spliced mRNA. Because the p12(I) protein is very hydrophobic and poorly immunogenic, we genetically engineered its cDNA by adding a short stretch of amino acids from the highly immunogenic epitope HA1 of influenza virus or the AU1 epitope of bovine papillomavirus. The HA1 epitope was also added to the p13(II) and p30(II) proteins, albeit rabbit immune sera raised against synthetic peptides were also available. To determine in which cellular compartments these proteins reside, we transfected the tagged and wild-type cDNAs in HeLa/Tat cells and studied their localization by indirect immunofluorescence. The p12(I) protein was identified in the cellular endomembranes and, particularly, in the perinuclear area. p13(II) and p30(II) were found in the nuclei and nucleoli of the transfected cells, respectively. The presence of the HA1 epitope at the carboxy terminus of p13(II) and p30(II) did not interfere with their cellular localization, since the rabbit immune sera demonstrated their presence in the same cellular compartments when the untagged proteins were expressed. The defined localization of these proteins in specific cellular compartments warrants further study of their function.
ASJC Scopus subject areas
- Insect Science