Main Difference – Positive vs Negative Sense RNA Virus
Viruses are the smallest form of obligate parasites that require a host cell for their replication. They consist of a DNA or RNA genome covered by a protein capsid. The viruses that consist of a genome made up of DNA are called DNA viruses while viruses made up of RNA are called RNA viruses. Positive and negative sense RNA viruses are the two types of single-stranded RNA viruses classified based on the type of genome. Positive sense RNA is also known as plus-strand or sense strand while negative sense RNA is also known as minus-strand or antisense strand. The main difference between positive and negative sense RNA virus is that positive sense RNA virus consists of viral mRNA that can be directly translated into proteins whereas negative sense RNA virus consists of viral RNA that is complementary to the viral mRNA.
Key Areas Covered
1. What is Positive Sense RNA Virus
– Definition, Protein Synthesis, Replication
2. What is Negative Sense RNA Virus
– Definition, Protein Synthesis, Replication
3. What are the Similarities Between Positive and Negative Sense RNA Virus
– Outline of Common Features
4. What is the Difference Between Positive and Negative Sense RNA Virus
– Comparison of Key Differences
Key Terms: mRNA, Negative Sense, Positive Sense, RNA-Dependent RNA Polymerase (RdRp), Single-Stranded RNA Virus, Transcription, Translation
What is Positive Sense RNA Virus
Positive sense RNA virus is a type of single-stranded RNA virus whose genetic material is viral mRNA that encodes for proteins. This means they contain the sense strand of RNA as their genome and it can be readily translated into proteins. Hence, positive sense RNA does not require an RNA polymerase packaged inside the virion. The 5’ end of the genome is either capped or naked while the 3’ end is polyadenylated or naked. Poliovirus, hepatitis C virus, dengue virus, SARS, West Nile virus, echovirus, and Coxsackie virus are examples of positive sense RNA viruses. An electron micrograph of hepatitis C virus is shown in figure 1.
Figure 1: Hepatitis C Virus
The replication of the positive sense RNA viruses occurs through the double-stranded RNA intermediate. Upon infection, the polyproteins encoded for the viral replication are translated. The replication of the single-stranded RNA leads to the formation of RNA duplex which in turn is transcribed into single-stranded positive genomic mRNA.
What is Negative Sense RNA Virus
Negative sense RNA virus refers to a type of single-stranded RNA virus whose genetic material is the antisense strand of the viral mRNA. Hence, the negative strand RNA viruses consist of a genome that is complementary to the viral mRNA. Therefore, the viral genome cannot be readily translated into viral proteins. Hence, the virion should be packed with an RNA-dependent RNA polymerase enzyme that aids in the transcription of viral RNA. Ebola virus, Rabies virus, mumps virus, influenza virus, and hepatitis D virus are examples of negative sense RNA viruses. An electron micrograph of influenza virus is shown in figure 2.
Figure 2: Influenza Virus
During replication, the RNA-dependent RNA polymerase complex binds to the antisense or leading strand, producing new viral RNA. The viral genome is encapsidated during the replication.
Similarities Between Positive and Negative Sense RNA Virus
- Both positive and negative sense RNA viruses consist of a single-stranded RNA genome.
- Both positive and negative sense RNA require a specific host for viral replication.
- Both positive and negative sense RNA viruses are infectious and cause diseases in animals and plants.
Difference Between Positive and Negative Sense RNA Virus
Definition
Positive Sense RNA Virus: Positive sense RNA virus is a type of single-stranded RNA viruses whose genetic material is viral mRNA that encodes for proteins.
Negative Sense RNA Virus: Negative sense RNA virus is a type of single-stranded RNA viruses whose genetic material is the antisense strand of the viral mRNA.
Type of Genome
Positive Sense RNA Virus: Positive sense RNA viruses are known to have a positive sense (5’ to 3’) RNA genome.
Negative Sense RNA Virus: Negative sense RNA viruses are known to have a negative sense (3’ to 5’) RNA genome.
Alternative Names
Positive Sense RNA Virus: Positive sense RNA is also called the plus-strand or sense strand.
Negative Sense RNA Virus: Negative sense RNA is also called the minus-strand or antisense strand.
Viral RNA
Positive Sense RNA Virus: Positive sense RNA virus consists of viral mRNA that can be readily translated into proteins.
Negative Sense RNA Virus: Negative sense RNA virus consists of viral mRNA complementary to the mRNA.
Trancription
Positive Sense RNA Virus: Positive sense RNA needs not be transcribed.
Negative Sense RNA Virus: Negative sense RNA should be transcribed into positive sense RNA before the translation.
RNA Polymerase
Positive Sense RNA Virus: Positive sense RNA viruses do not require RNA polymerase.
Negative Sense RNA Virus: Negative sense RNA viruses require RNA-dependent RNA polymerase for the transcription of the genome into positive sense RNA.
Replication
Positive Sense RNA Virus: Positive sense RNA viruses replicate via a double-stranded RNA intermediate.
Negative Sense RNA Virus: The replication of the negative strand RNA virus genome occurs with the aid of RNA-dependent RNA polymerase.
Examples
Positive Sense RNA Virus: Poliovirus, echovirus, and Coxsackie virus are examples of positive sense RNA viruses.
Negative Sense RNA Virus: Ebola virus, Rabies virus, mumps virus, influenza virus, and hepatitis D virus are examples of negative sense RNA viruses.
Conclusion
Positive and negative sense RNA viruses are the two types of ssRNA viruses. Positive sense RNA viruses have a genome containing viral mRNA that can be readily translated into proteins. However, negative sense RNA viruses consist of a genome containing viral RNA that is complementary to the mRNA. Hence, it should be transcribed into positive sense RNA prior to the translation with the help of RNA polymerase. The main difference between positive and negative sense RNA virus is the type of viral RNA present in the genome.
Reference:
1.“Definition of Positive-Strand RNA virus.” MedicineNet, Available here.
2.“Positive stranded RNA virus replication.” Viralzone, Available here.
3.“Negative sense RNA viruses.” MicrobiologyBytes, 4 Feb. 2008, Available here.
4.“Negative stranded RNA virus replication.” Viralzone, Available here.
Image Courtesy:
1. “HCV EM picture 2” By HCV_pictures.png: Maria Teresa Catanese, Martina Kopp, Kunihiro Uryu , and Charles Ricederivative work: TimVickers (talk) – HCV_pictures.png, Public Domain) via Commons Wikimedia
2. “Influenza virus particle 8430 lores” By Cynthia Goldsmith – CDC/ Dr. Erskine. L. Palmer; Dr. M. L. Martin from the Centers for Disease Control and Prevention’s Public Health Image Library (PHIL) (Public Domain) via Commons Wikimedia
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