Structural features in TAR RNA of human and simian immunodeficiency viruses: a phylogenetic analysis.

A comparative analysis of TAR RNA structures in human and simian immunodeficiency viruses reveals the conservation of certain structural features despite the divergence in sequence. Both the TAR elements of HIV-1 and SIV-chimpanzee can be folded into relatively simple one-stem hairpin structures. Chemical and RNAase probes were used to analyze the more complex structure of HIV-2 TAR RNA, which folds into a branched hairpin structure. A surprisingly similar RNA conformation can be proposed for SIV-mandrill, despite considerable divergence in nucleotide sequence. A third structural presentation of TAR sequences is seen for SIV-african green monkey. These results are generally consistent with the classification of HIV-SIV viruses in four subgroups based on sequence analyses (both nucleotide- and amino acid-sequences). However, some conserved TAR structures were detected for members of different virus subgroups. It is therefore proposed that RNA structure analysis might provide an additional tool for determining phylogenetic relationships among the HIV-SIV viruses.