Ambisense

Ambisense

Ambisense is a term used in molecular biology to describe a type of viral genome organization. In ambisense genomes, both the positive-sense and negative-sense strands of RNA are used to encode proteins. This unique feature is found in some single-stranded RNA viruses, particularly within the Arenaviridae and Bunyaviridae families.

Structure and Function

Ambisense RNA viruses have a genome that is partially positive-sense and partially negative-sense. This means that one part of the RNA strand can be directly translated into proteins (positive-sense), while the other part must first be transcribed into a complementary RNA strand before translation (negative-sense).

In the case of ambisense viruses, the genome is typically segmented. Each segment contains both positive-sense and negative-sense regions. The positive-sense region is usually located at one end of the segment, while the negative-sense region is at the other end. This arrangement allows the virus to efficiently regulate the expression of its genes during the infection cycle.

Examples of Ambisense Viruses

Some well-known viruses with ambisense genomes include:

• Lassa virus: A member of the Arenaviridae family, Lassa virus is responsible for Lassa fever, a type of viral hemorrhagic fever.
• Rift Valley fever virus: Belonging to the Bunyaviridae family, this virus causes Rift Valley fever, which affects both humans and livestock.

Mechanism of Gene Expression

In ambisense viruses, gene expression is tightly regulated. The transcription of the negative-sense region into a positive-sense RNA is often controlled by the presence of specific promoter sequences and the activity of viral RNA-dependent RNA polymerase. Once transcribed, the positive-sense RNA can be translated by the host cell's ribosomes to produce viral proteins.

The ambisense strategy allows these viruses to maximize their coding capacity within a limited genome size, which is a common evolutionary adaptation among RNA viruses.

Also see

• Positive-sense single-stranded RNA virus
• Negative-sense single-stranded RNA virus
• Viral replication
• RNA virus