Orthoreovirus (taxid:10882)



Non enveloped, icosahedral virion with a double capsid structure, about 80 nm in diameter. Pentameric turrets sit on the outside of the innermost capsid. The outer capsid has a T=13 icosahedral symmetry, the inner capsid a T=2* icosahedral symmetry.
Virion maturation schemes image



Segmented dsRNA linear genome. Contains 10 segments: L1, L2, L3, M1, M2, M3, S1, S2, S3, S4, coding for 12-13 proteins. Segments size range from 1,189 to 3,916nt (MRV-3De). Genome total size is 23.5 Kb (MRV-3De). MuNSC and S.1s are produced by leaky scanning of mRNA M3 and S1 respectively.


The dsRNA genome is never completely uncoated, to prevent activation of antiviral state by the cell in response to dsRNA. The viral polymerase lambda3 synthesizes a capped and non-polyadenylated monocistronic mRNA from each dsRNA segment. These capped mRNAs are translocated to the cell cytoplasm where they are translated.




  1. Attachment to host receptors mediates clathrin-mediated endocytosis of virus into host cell.
  2. Particles are partially uncoated in endolysosomes, but not entirely, and penetrate in the cytoplasm.
  3. Early transcription of the dsRNA genome by viral polymerase occurs inside this sub-viral particle (naked core), so that dsRNA is never exposed to the cytoplasm.
  4. Full-length plus-strand transcripts from each of the dsRNA segments are synthesized. These plus-strand transcripts are used as templates for translation.
  5. Viral proteins and genomic RNAs aggregates in cytoplasmic viral factories.
  6. (+)RNAs are encapsidated in a sub-viral particle, in which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
  7. The capsid is assembled on the sub-viral particle.
  8. Mature virions are released presumably following cell death and associated breakdown of host plasma membrane.

Host-virus interaction

Apoptosis modulation

Mammalian reovirus mediates host cell apoptosis through the activation of death receptors, including TRAIL, TNFR and Fas . Activation of these death receptors induces the activation downstream caspases (caspase-3).

Avian orthoreovirus induces host cell apoptosis probably through upregulation of p53 (activation of DNA-damage signalling) by viral sigmaC protein .

Autophagy modulation

Avian orthoreovirus also seems to induces autophagy .

Innate immune response inhibition

Mammalian orthoreoreovirus σ3 protein binds to dsRNA and inhibits the PRK-mediated antiviral response of the host cell .
Mammalian orthoreovirus &mu2; protein from strain Lang (T1L) inhibits IFN-beta-induced reporter gene expression .

Avian orthoreovirus σA protein binds to dsRNA and inhibits the PRK-mediated antiviral response of the host cell .

Cell-cycle modulation

Human and avian reovirus induce G2/M cell cycle arrest .

Matching UniProtKB/Swiss-Prot entries

(all links/actions below point to uniprot.org website)

34 entries grouped by strain

11 entries

Reovirus type 1 (strain Lang) (T1L) (Mammalian orthoreovirus 1) reference strain

MU1_REOVL Outer capsid protein mu-1 (Mu1) [Cleaved into: Outer capsid protein mu-1N; Outer capsid protein ...
MUNS_REOVL Protein mu-NS (MuNS)
SIGM1_REOVL Outer capsid protein sigma-1 (Sigma1) (Cell attachment protein) (Hemagglutinin)
SIGM3_REOVL Outer capsid protein sigma-3 (Sigma3)
SIGNS_REOVL Protein sigma-NS (SigmaNS)
RDRP_REOVL RNA-directed RNA polymerase lambda-3 (Lambda3) (EC (Lambda3(Pol))
MU2_REOVL Microtubule-associated protein mu-2 (Mu2)
LMBD2_REOVL Outer capsid protein lambda-2 (Lambda2) (Lambda2(Cap)) [Includes: mRNA guanylyltransferase (EC ...
LMBD1_REOVL Inner capsid protein lambda-1 (Lambda1) (EC (ATP-dependent DNA helicase lambda-1) ...
SIG1S_REOVL Protein sigma-1-small (Sigma1s) (Sigma-s) (Sigma1NS) (Sigma1bNS) (p14)
SIGM2_REOVL Inner capsid protein sigma-2 (Sigma2)

11 entries

Reovirus type 2 (strain D5/Jones) (T2J) (Mammalian orthoreovirus 2)

MU1_REOVJ Outer capsid protein mu-1 (Mu1) [Cleaved into: Outer capsid protein mu-1N; Outer capsid protein ...
SIGM1_REOVJ Outer capsid protein sigma-1 (Sigma1) (Cell attachment protein) (Hemagglutinin)
SIGNS_REOVJ Protein sigma-NS (SigmaNS)
RDRP_REOVJ RNA-directed RNA polymerase lambda-3 (Lambda3) (EC (Lambda3(Pol))
SIGM3_REOVJ Outer capsid protein sigma-3 (Sigma3)
LMBD2_REOVJ Outer capsid protein lambda-2 (Lambda2) (Lambda2(Cap)) [Includes: mRNA guanylyltransferase (EC ...
MUNS_REOVJ Protein mu-NS (MuNS)
LMBD1_REOVJ Inner capsid protein lambda-1 (Lambda1) (EC (ATP-dependent DNA helicase lambda-1) ...
SIG1S_REOVJ Protein sigma-1-small (Sigma1s) (Sigma-s) (Sigma1NS) (Sigma1bNS) (p14)
SIGM2_REOVJ Inner capsid protein sigma-2 (Sigma2)
MU2_REOVJ Microtubule-associated protein mu-2 (Mu2)

11 entries

Reovirus type 3 (strain Dearing) (T3D) (Mammalian orthoreovirus 3)

MU1_REOVD Outer capsid protein mu-1 (Mu1) [Cleaved into: Outer capsid protein mu-1N; Outer capsid protein ...
LMBD2_REOVD Outer capsid protein lambda-2 (Lambda2) (Lambda2(Cap)) [Includes: mRNA guanylyltransferase (EC ...
SIGM3_REOVD Outer capsid protein sigma-3 (Sigma3)
SIGM1_REOVD Outer capsid protein sigma-1 (Sigma1) (Cell attachment protein) (Hemagglutinin)
MUNS_REOVD Protein mu-NS (MuNS)
LMBD1_REOVD Inner capsid protein lambda-1 (Lambda1) (EC (ATP-dependent DNA helicase lambda-1) ...
SIGNS_REOVD Protein sigma-NS (SigmaNS)
RDRP_REOVD RNA-directed RNA polymerase lambda-3 (Lambda3) (EC (Lambda3(Pol))
SIGM2_REOVD Inner capsid protein sigma-2 (Sigma2)
SIG1S_REOVD Protein sigma-1-small (Sigma1s) (Sigma-s) (Sigma1NS) (Sigma1bNS) (p14)
MU2_REOVD Microtubule-associated protein mu-2 (Mu2)

1 entry

Avian reovirus (strain S1133) (ARV)

SIGC_ARVS1 Sigma-C capsid protein (Sigma-3 protein)
These structures were created with the help of Colabfold by Jason Nomburg, Nathan Price and Jennifer Doudna (ModelArchive).

Baboon orthoreovirus taxid:75888

Protein ModelArchive
Major inner capsid protein sigma 1 ma-jd-viral-16784
Major nonstructural protein ma-jd-viral-41549
Major outer capsid protein sigma 2 ma-jd-viral-14815
Minor core protein ma-jd-viral-09891
Nonstructural protein sigma NS ma-jd-viral-04460
Outer shell protein ma-jd-viral-29634

Broome reovirus taxid:667093

Protein ModelArchive
Core protein ma-jd-viral-09890
Core protein (Major inner capsid protein sigma 1) ma-jd-viral-16783
Major outer capsid protein ma-jd-viral-14816
Major outer capsid protein ma-jd-viral-29639
Mu-class non-structural protein ma-jd-viral-41551
Sigma-class non-structural protein ma-jd-viral-04462
Small non-structural protein p13 ma-jd-viral-50498
Small non-structural protein p16 ma-jd-viral-53519

Cangyuan orthoreovirus taxid:1388882

Protein ModelArchive
Guanylytransferase ma-jd-viral-31465
Inner capsid protein ma-jd-viral-12645
Major inner capsid protein ma-jd-viral-16788
Major outer capsid ma-jd-viral-14814
Major outer capsid ma-jd-viral-29640
Minor inner capsid ma-jd-viral-09893
Nonstructural protein ma-jd-viral-04465
Nonstructural protein ma-jd-viral-41554
RNA-directed RNA polymerase (EC ma-jd-viral-19859
Sigma C capsid protein ma-jd-viral-09461

Mammalian orthoreovirus 3 taxid:538123

Protein ModelArchive
Mu-1 protein ma-jd-viral-29635
Mu-2 protein ma-jd-viral-09888
Mu-NS protein ma-jd-viral-41550
Sigma-1 protein ma-jd-viral-29164
Sigma-2 protein ma-jd-viral-16785
Sigma-3 protein ma-jd-viral-57645
Sigma-NS protein ma-jd-viral-04461

Reptilian orthoreovirus taxid:226613

Protein ModelArchive
Lambda A ma-jd-viral-12646
Lambda C ma-jd-viral-31464
MuA ma-jd-viral-09889
MuNS ma-jd-viral-41548
RNA-directed RNA polymerase (EC ma-jd-viral-19854
Sigma C ma-jd-viral-09460
SigmaA ma-jd-viral-16787
p14 ma-jd-viral-31771