V. Ciminale et al., CODING POTENTIAL OF THE X-REGION OF HUMAN T-CELL LEUKEMIA LYMPHOTROPIC VIRUS TYPE-II/, Journal of acquired immune deficiency syndromes and human retrovirology, 13, 1996, pp. 220-227
Human T-cell leukemia/lymphotropic viruses type I and type II (HTLV-I
and HTLV-II) are complex human retroviruses showing a similar genetic
organization but substantially different biologic and pathogenic prope
rties. As in other complex retroviruses, the 3' portion of the HTLV ge
nome contains the peculiar ''X region'' comprising several partially o
verlapping open reading frames (ORFs). To search for a possible basis
for the pathogenic differences between the two viruses, a number of st
udies have been carried out to analyze the coding potential of the X r
egion of HTLV-I and, more recently, of HTLV-II. This review focuses on
the coding potential or the HTLV-II X region and presents a compariso
n with that of HTLV-I. Expression of different ORFs present in the X r
egion may be accessed through two expression strategies: alternative s
plicing and translation of more than one protein from the same mRNA. I
nitial analyses of the X region proteins indicate that some differ sig
nificantly from their HTLV-I homologues, thus providing possible clues
to the understanding of the complex life cycle and pathogenicity of t
he two viruses.