SIMIAN T-CELL LEUKEMIA-VIRUS TYPE-I FROM NATURALLY INFECTED FERAL MONKEYS FROM CENTRAL AND WEST-AFRICA ENCODES A 91-AMINO ACID P12 (ORF-I) PROTEIN AS OPPOSED TO A 99-AMINO ACID PROTEIN ENCODED BY HTLV TYPE-I FROM HUMANS

A single protein of 12 kDa, p12 is encoded by the HTLV-I genome from b oth the singly spliced mRNA pX-ORF-I and doubly spliced mRNA pX-rex-OR F-I, While many full-length sequences of HTLV-1 are known, data on the p12 region of African STLV-I are unavailable. We have undertaken to s equence the p12 gene in STLV-I from Central and West African naturally infected primates, and have compared them to known p12 sequences of H TLV-I, Our data on sequence and in vitro transcription-translation ana lyses indicate that p12 is a 91-amino acid (aa) protein among STLV-I s trains from Central and West Africa, in contrast to the 99-aa protein found among HTLV-I strains around the globe, The p12 sequences of STLV -I exhibit a marked genetic variability at the level of both nucleotid e and peptide sequences. Hydropathic and helical wheel analyses reveal that 60% of residues in HTLV-I p12 are hydrophobic, in contrast to 55 % in STLV-I from Africa. Although HTLV-I and STLV-I show a similar put ative antigenic site, a second potential site was located exclusively in STLV-I from Africa, There are differences in the predicted transmem brane domains in p12 between STLV-I and HTLV-I, Furthermore, the secon dary structure data according to the Chou and Fasman algorithm predict an alpha-helical domain at the carboxy terminus in HTLV-I, and this: domain may be truncated in STLV-I p12, The amino acid sequence of p12 shows two leucine zipper moths (LZMs) at the amino terminus and in the middle region, respectively, This is the first report describing the size differences in p12 protein between HTLV-I and STLV-I, which may p rovide insights into pathogenic mechanisms used by HTLV-I and STLV-I.