The use of DNA and RNA oligonucleotides in hybrid structures with longer polynucleotide chains to probe the structural requirements for moloney murine leukemia virus plus strand priming.

Plus strand priming during retroviral reverse transcription requires specific cleavage within the polypurine tract of the viral genome by the reverse transcriptase-associated RNase H. Previously it has been shown that a 190-base RNA-DNA hybrid containing the Moloney murine leukemia virus polypurine tract can serve as a substrate for the priming reaction. To investigate the structural requirements for the reaction, a series of DNA oligonucleotides was hybridized to the 190-base single-stranded RNA and tested as substrates for RNase H. At low enzyme concentrations, the sites of cleavage are located 17-23 nucleotides from the 3'-end of the DNA oligonucleotide, consistent with the observations of others that binding of the DNA polymerase at a primer terminus fixes the position of cleavage by RNase H. At higher enzyme concentrations, additional cleavages are observed in the RNA 3' of these sites, but there is no preference for cleavage at the plus strand origin. In contrast to the results with DNA oligonucleotides, hybridization of RNA oligonucleotides containing the polypurine tract to the 190-base single-stranded DNA generates substrates that are cleaved at the origin and efficiently extended into DNA. An RNA oligonucleotide hybridized downstream of the polypurine tract is cleaved but not extended. These results support the view that RNase H cleavage to generate the plus strand primer is uncoupled from minus strand DNA synthesis.

The majority of simian immunodeficiency virus/mne circle junctions result from ligation of unintegrated viral DNA ends that are aberrant for integration.

SIV/Mne circle junctions were amplified by the polymerase chain reaction (PCR) and cloned in a bacterial plasmid. Sequence analysis of clones isolated from 11 independent PCRs reveals that the start site for plus DNA synthesis is 5' ACTG. . ., and thus an asymmetric cleavage must occur during viral integration. In addition, most of the sequences found resulted from the ligation of aberrant proviral DNA ends that were apparently generated by priming errors, primer removal errors, or integrase processing errors. The results suggest that in this virus, as in Moloney murine leukemia virus, two good ends may be required for efficient integration.

Phenomenology and course of psychiatric disorders associated with combat-related posttraumatic stress disorder.

OBJECTIVE: Studies indicate that chronic combat-related posttraumatic stress disorder (PTSD) is frequently associated with other psychiatric disorders. Questions regarding the nature and interrelationships of these conditions require clarification. The purpose of this study was to address primary and secondary illness relationships by focusing on the specific phenomenology and course of illness onset of PTSD comorbidity. METHOD: In order to minimize confounding factors, only outpatients without recent substance use disorders were included. Sixty subjects who had been exposed to severe combat stress including veterans of Vietnam and veterans of World War II or Korea, 15 of whom were former prisoners of war, received structured assessments over serial evaluations. RESULTS: PTSD was the most prevalent lifetime disorder followed by major depression, panic disorder, generalized anxiety disorder, and phobic disorder or symptoms. Endogenous-appearing features overlapping other clinical populations were common; however, some specific symptom patterns also were suggestive of traumatic influence. Unlike generalized anxiety disorder and past substance use, the mean onset of phobias, major depression, and panic disorder, respectively, occurred later than PTSD. CONCLUSIONS: These observations suggest that persistent conditions related to PTSD progress toward symptoms that are increasingly autonomous in their pattern of occurrence.