Expression and functional properties of proteins encoded in the x-II ORF of HTLV-I

Virus Res. 2001 Oct 30;78(1-2):35-43. doi: 10.1016/s0168-1702(01)00282-9.


With the aim of identifying viral proteins that contribute to the distinctive properties of HTLV-I biology and pathogenicity, several laboratories have investigated the coding potential of the X region of the genome, which includes five partially overlapping open reading frames (ORFs). We and others have shown that, in addition to the essential regulatory proteins Rex and Tax, a number of accessory proteins encoded in the X region can be produced by alternative splicing and multicistronic translation. One X region ORF, termed X-II, produces two protein isoforms named Tof/p30II and p13II, which are expressed from a doubly- and singly-spliced mRNA, respectively. Initial functional analyses demonstrated that Tof/p30II is a nucleolar/nuclear protein that possesses a region capable of binding to RNA, and p13II is a mitochondrial protein that alters the morphology and function of this organelle. Together with data from other laboratories demonstrating the production of antibodies and CTL against x-II ORF products in HTLV-I infected subjects and the requirement of this ORF for efficient viral replication in vivo, these findings suggest that further characterization of Tof/p30II and p13II will yield insight into remaining undefined aspects of HTLV-I pathogenicity and replication.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Gene Expression
  • Genes, pX / physiology*
  • Human T-lymphotropic virus 1 / genetics*
  • Human T-lymphotropic virus 1 / metabolism
  • Mitochondria / metabolism
  • Molecular Sequence Data
  • Open Reading Frames
  • RNA Splicing
  • RNA, Messenger / metabolism
  • RNA-Binding Proteins / metabolism
  • Retroviridae Proteins / genetics*
  • Retroviridae Proteins / metabolism


  • RNA, Messenger
  • RNA-Binding Proteins
  • Retroviridae Proteins
  • tof protein, Human T-lymphotropic virus 1