The DTS showed good reliability and validity, and offers promised as a scale which is particularly suited to assessing symptom severity, treatment outcome and in screening for the likely diagnosis of PTSD.

Our comparison of deduced amino acid sequences for retroviral/retrotransposon integrase (IN) proteins of several organisms, including Drosophila melanogaster and Schizosaccharomyces pombe, reveals strong conservation of a constellation of amino acids characterized by two invariant aspartate (D) residues and a glutamate (E) residue, which we refer to as the D,D(35)E region. The same constellation is found in the transposases of a number of bacterial insertion sequences. The conservation of this region suggests that the component residues are involved in DNA recognition, cutting, and joining, since these properties are shared among these proteins of divergent origin. We introduced amino acid substitutions in invariant residues and selected conserved and nonconserved residues throughout the D,D(35)E region of Rous sarcoma virus IN and in human immunodeficiency virus IN and assessed their effect upon the activities of the purified, mutant proteins in vitro. Changes of the invariant and conserved residues typically produce similar impairment of both viral long terminal repeat (LTR) oligonucleotide cleavage referred to as the processing reaction and the subsequent joining of the processed LTR-based oligonucleotides to DNA targets. The severity of the defects depended upon the site and the nature of the amino acid substitution(s). All substitutions of the invariant acidic D and E residues in both Rous sarcoma virus and human immunodeficiency virus IN dramatically reduced LTR oligonucleotide processing and joining to a few percent or less of wild type, suggesting that they are essential components of the active site for both reactions. On the basis of similarities with enzymes that catalyze analogous reactions, we propose that the invariant D and E residues may participate in coordination of the metal cofactor (Mn2+ or Mg2') required for the catalytic activities of IN. We further speculate that a metal-DNA complex may be necessary to position both LTR and target DNA substrates for nucleophilic attack during the cleavage and joining reactions.Retroviral integration is dependent upon the interaction of three macromolecular components: (i) a virus-encoded protein, integrase (IN), (ii) specific sequences at the long terminal repeat (LTR) termini of viral "donor" DNA, and (iii) a host DNA "target." Results from the study of several different retroviral systems reveal a stepwise pathway for the interaction of these components during integration in a natural virus infection: (i) removal of a dinucleotide from the 3' ends of linear viral DNA (4) in the cytoplasm, which we refer to as the processing reaction, (ii) migration of the viral DNA to the cell nucleus within a higher-order protein complex (2), (iii) staggered cleavage of host DNA generating 5'-strand extensions, likely coupled to single-strand joining of the processed 3' hydroxyl ends of viral DNA to the 5' phosphate ends of the host target DNA, and (iv) repair and ligation of the gapped unjoined opposite strands. This final step produces a short duplication of host seq...

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We have reviewed the current state of knowledge concerning the three enzymes common to all retroviruses. It is informative to consider them together, since their activities are interrelated. The enzymatic activities of RT and IN depend on processing of polyprotein precursors by PR. Furthermore, RT produces the viral DNA substrate to be acted upon by IN. All three of these retroviral enzymes function as multimers, and it is conceivable that specific polyprotein precursor interactions facilitate the multimerization of all of them. The multimeric structures of the enzymes are, however, quite different. PR is a symmetric homodimer whose subunits contribute to formation of a single active site. RT (of HIV, at least) is an asymmetric heterodimer in which one subunit appears to contribute all of the catalytic activity and the second is catalytically inactive, but structurally important. IN also functions minimally as a dimer for processing and joining. The retroviral enzymes represent important targets for antiviral therapy. Considerable effort continues to be focused on developing PR and RT inhibitors. As more is learned about IN, such efforts can be extended. Since these enzymes are critical at different stages in the retroviral life cycle, one optimistic hope is that a combination of drugs that target all of them may be maximally effective as therapy for AIDS.

Retroviral DNA integration is catalyzed by the viral protein integrase. Here, it is shown that DNA-dependent protein kinase (DNA-PK), a host cell protein, also participates in the reaction. DNA-PK-deficient murine scid cells infected with three different retroviruses showed a substantial reduction in retroviral DNA integration and died by apoptosis. Scid cell killing was not observed after infection with an integrase-defective virus, suggesting that abortive integration is the trigger for death in these DNA repair-deficient cells. These results suggest that the initial events in retroviral integration are detected as DNA damage by the host cell and that completion of the integration process requires the DNA-PK-mediated repair pathway.

Integration of retroviral DNA into the host chromosome requires a virus-encoded integrase (IN). IN recognizes, cuts and then joins specific viral DNA sequences (LTR ends) to essentially random sites in host DNA. We have used computer-assisted protein alignments and mutagenesis in an attempt to localize these functions within the avian retroviral IN protein. A comparison of the deduced amino acid sequences for 80 retroviral/retrotransposon IN proteins reveals strong conservation of an HHCC N-terminal 'Zn finger'-like domain, and a central D(35)E region which exhibits striking similarities with sequences deduced for bacterial IS elements. We demonstrate that the HHCC region is not required for DNA binding, but contributes to specific recognition of viral LTRs in the cutting and joining reactions. Deletions which extend into the D(35)E region destroy the ability of IN to bind DNA. Thus, we propose that the D(35)E region may specify a DNA-binding/cutting domain that is conserved throughout evolution in enzymes with similar functions.

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The purified integration protein (IN) of avian myeloblastosis virus is shown to nick double-stranded oligodeoxynucleotide substrates that mimic the ends of the linear form of viral DNA. In the presence of Mg2+, nicks are created 2 nucleotides from the 3' OH ends of both the U5 plus strand and the U3 minus strand. Similar cleavage is observed in the presence of Mn2' but only when the extent of the reaction is limited. Neither