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Viral-encoded small RNAs in herpes virus saimiri induced tumors
Abstract:
DNA sequences from the left terminus of herpes virus saimiri L-DNA are essential for the oncogenic and transforming potential of the virus, but these sequences are not required for replication. RNA derived from 0.0 to 6.7 map units (7.4 kbp) on the herpes virus saimiri genome was studied by Northern blot hybridization and by nuclease protection analyses. Although several poly(A)-containing RNAs were detected from this region in permissively-infected monolayer cells in vitro, these RNAs could not be detected in cells taken directly from viral-induced lymphomas nor in the lymphoblastoid tumor cell line 1670. Instead, these transformed T-cells expressed four small RNAs of approximately 73, 105, 110 and 135 nt derived from this region. These small RNAs were not detected at all during the course of lytic infection of monolayer cells. Thus, synthesis of these RNAs is stringently regulated in a cell-type specific manner. Genomic coding sequences for each of these small RNAs were mapped to 0.5-1.2 kbp DNA fragments stretched over 4.3 kbp of viral genetic information. These findings together with the biological properties of mutants with deletions in this region have led us to speculate that one or more of these small RNAs play an essential role in cell growth transformation by herpes virus saimiri.
Insights
Herpesvirus saimiri oncogenesis involves specific small RNAs, not replication-dependent RNAs, in transformed cells. These novel viral small RNAs are crucial for herpesvirus saimiri
Area of Science:
- Virology
- Molecular Biology
- Oncology
Background:
- Herpesvirus saimiri (HVS) possesses oncogenic and transforming potential linked to its left terminus L-DNA sequences.
- These critical DNA sequences are not essential for viral replication, suggesting a distinct role in pathogenesis.
Purpose of the Study:
- To investigate the RNA transcripts originating from the 0.0 to 6.7 map units (7.4 kbp) region of the HVS genome.
- To identify and characterize viral RNAs present in HVS-induced lymphomas and transformed cell lines versus lytically infected cells.
Main Methods:
- Northern blot hybridization to detect and analyze RNA species.
- Nuclease protection assays to precisely map RNA transcripts.
- Genomic DNA mapping to locate coding sequences for identified small RNAs.
Main Results:
- Large poly(A)-containing RNAs were detected in vitro but absent in HVS-induced lymphomas and lymphoblastoid cells.
- Transformed T-cells exclusively expressed four small RNAs (approx. 73, 105, 110, and 135 nt) from this genomic region.
- These small RNAs were undetectable during lytic HVS infection, indicating cell-type specific regulation.
- Coding sequences for these small RNAs were mapped across a 4.3 kbp viral DNA segment.
Conclusions:
- The expression of specific small RNAs from the HVS left terminus is tightly regulated and cell-type specific.
- These novel viral small RNAs are preferentially synthesized in transformed cells, not during lytic infection.
- It is hypothesized that one or more of these small RNAs are essential for HVS-mediated cell growth transformation and oncogenesis.