Related Experiment Videos
A very small viral double-stranded RNA
T H Chang1, N Banerjee, J Bruenn
1Department of Biology, California Institute of Technology, Pasadena 91125.
Abstract:
UmV is a double-stranded RNA (dsRNA) virus of the corn fungal pathogen Ustilago maydis. UmV has no infectious cycle. Some UmV subtypes have viral dsRNAs encoding secreted toxins that kill sensitive cells of the same species and related species. There are three viral subtypes, P1, P4 and P6, which differ in the specificity of their secreted killer toxins. Each has three size classes of dsRNA: H (heavy), M (medium) and L (light). The L segments of UmV are unique in being derived from one end of the larger M segments. We have sequenced P1 L and placed it at the 3' end of the P1 M1 plus strand. In their overlapping regions, these dsRNAs are identical in sequence. In vitro translation of P1 M1 results in a peptide whose size is consistent with its being encoded by the non-L region of M1. P1 L is a very small dsRNA of 355 bp. It has no long open reading frames and produces no detectable in vitro translation product. The sequence of P1 L suggests that it is derived by a process unique among dsRNA viruses: replication and packaging of the 3' end fragment of a processed mRNA.
Insights
The Ustilago maydis virus (UmV) P1 L dsRNA segment is derived from the 3' end of the M segment. This unique process involves replicating and packaging a processed mRNA fragment, unlike other dsRNA viruses.
Area of Science:
- Virology
- Mycology
- Molecular Biology
Background:
- Ustilago maydis (UmV) is a double-stranded RNA virus infecting the corn fungal pathogen Ustilago maydis.
- UmV subtypes P1, P4, and P6 produce distinct killer toxins, affecting sensitive cells within and between species.
- UmV possesses three dsRNA size classes: H, M, and L, with L segments uniquely originating from M segments.
Purpose of the Study:
- To sequence and characterize the P1 L dsRNA segment of UmV.
- To elucidate the origin and replication mechanism of the P1 L dsRNA segment.
- To understand the unique relationship between M and L dsRNA segments in UmV.
Main Methods:
- DNA sequencing of the P1 L dsRNA segment.
- Sequence alignment to determine its relationship with the M segment.
- In vitro translation assays to assess protein coding potential.
Main Results:
- The P1 L dsRNA segment was sequenced and mapped to the 3' end of the P1 M1 plus strand.
- Overlapping regions between P1 L and P1 M1 dsRNAs showed identical sequences.
- P1 L (355 bp) lacks significant open reading frames and produced no in vitro translation product, while P1 M1 encoded a peptide from its non-L region.
Conclusions:
- The P1 L dsRNA segment is derived from the 3' end of the M segment, likely through a novel mechanism.
- This process involves the replication and packaging of a processed mRNA 3' end fragment.
- This represents a unique dsRNA virus replication strategy not observed in other known dsRNA viruses.