Disrupting MLV integrase:BET protein interaction biases integration into quiescent chromatin and delays but does not eliminate tumor activation in a MYC/Runx2 mouse model.

Murine leukemia virus (MLV) integrase (IN) lacking the C-terminal tail peptide (TP) loses its interaction with the host bromodomain and extraterminal (BET) proteins and displays decreased integration at promoter/enhancers and transcriptional start sites/CpG islands. MLV lacking the IN TP via an altered open reading frame was used to infect tumorigenesis mouse model (MYC/Runx2) animals to observe integration patterns and phenotypic effects, but viral passage resulted in the restoration of the IN TP through small deletions. Mice subsequently infected with an MLV IN lacking the TP coding sequence (TP-) showed an improved median survival by 15 days compared to wild type (WT) MLV infection. Recombination with polytropic endogenous retrovirus (ERV), Pmv20, was identified in seven mice displaying both fast and slow tumorigenesis, highlighting the strong selection within the mouse to maintain the full-length IN protein. Mapping the genomic locations of MLV in tumors from an infected mouse with no observed recombination with ERVs, TP-16, showed fewer integrations at TSS and CpG islands, compared to integrations observed in WT tumors. However, this mouse succumbed to the tumor in relatively rapid fashion (34 days). Analysis of the top copy number integrants in the TP-16 tumor revealed their proximity to known MLV common insertion site genes while maintaining the MLV IN TP- genotype. Furthermore, integration mapping in K562 cells revealed an insertion preference of MLV IN TP- within chromatin profile states associated with weakly transcribed heterochromatin with fewer integrations at histone marks associated with BET proteins (H3K4me1/2/3, and H3K27Ac). While MLV IN TP- showed a decreased overall rate of tumorigenesis compared to WT virus in the MYC/Runx2 model, MLV integration still occurred at regions associated with oncogenic driver genes independently from the influence of BET proteins, either stochastically or through trans-complementation by functional endogenous Gag-Pol protein.

Detection and molecular characterization of double-stranded RNA viruses in Philippine Trichomonas vaginalis isolates.

BACKGROUND/PURPOSE: The flagellated protozoon Trichomonas vaginalis that parasitizes the urogenital tract of humans was reported to harbor double-stranded RNA (dsRNA) viruses. These viruses, identified as Trichomonas vaginalis virus (TVV), belong to the genus Trichomonasvirus of the family Totiviridae. Four species, formally recognized by the International Committee on Taxonomy of Viruses (ICTV), have been reported and distinguished by pairwise comparisons of the sequences of genes coding for major capsid protein (CP) and RNA-dependent RNA polymerase (RdRp). METHODS: Reverse transcription polymerase chain reaction (RT-PCR) was used to amplify the complimentary DNA of target virus genes coding for CP and RdRp. Sequence analyses confirmed the identity of the TVV isolates from T. vaginalis cultures. RESULTS: A total of 35 dsRNA viruses were identified from 18 (19%) T. vaginalis isolates. Multiple TVV species were observed in six of the 18 T. vaginalis cultures. Phylogenetic analyses show monophyly in TVV1 and TVV2 whereas TVV3 and TVV4 appear paraphyletic. The phylogeny of Philippine Trichomonasvirus reflects the global distribution of its host. CONCLUSION: This is the first study in the Philippines and one of the two reports worldwide to detect the four TVVs and their concurrent infection in a single T. vaginalis isolate.