Research

Comparisons of the M1 genome segments and encoded μ2 proteins of different reovirus isolates

Peng Yin^1,2 , Natalie D Keirstead^1,3 , Teresa J Broering^4,5 , Michelle M Arnold^4,6 , John SL Parker^4,7 , Max L Nibert^4,6 and Kevin M Coombs¹

¹  Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, R3E 0W3 Canada

²  Thrasos Therapeutics, Hopkinton, MA 01748 USA

³  Department of Pathobiology, Ontario Veterinary College, Guelph, ON, N1G 2W1 Canada

⁴  Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA, 02115 USA

⁵  Massachusetts Biologic Laboratories, Jamaica Plain, MA 02130-3597 USA

⁶  Virology Training Program, Division of Medical Sciences, Harvard University, Cambridge, MA 02138 USA

⁷  James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853 USA

author email corresponding author email

Virology Journal 2004, 1:6doi:10.1186/1743-422X-1-6

Published:	23 September 2004

Abstract

Background

The reovirus M1 genome segment encodes the μ2 protein, a structurally minor component of the viral core, which has been identified as a transcriptase cofactor, nucleoside and RNA triphosphatase, and microtubule-binding protein. The μ2 protein is the most poorly understood of the reovirus structural proteins. Genome segment sequences have been reported for 9 of the 10 genome segments for the 3 prototypic reoviruses type 1 Lang (T1L), type 2 Jones (T2J), and type 3 Dearing (T3D), but the M1 genome segment sequences for only T1L and T3D have been previously reported. For this study, we determined the M1 nucleotide and deduced μ2 amino acid sequences for T2J, nine other reovirus field isolates, and various T3D plaque-isolated clones from different laboratories.

Results

Determination of the T2J M1 sequence completes the analysis of all ten genome segments of that prototype. The T2J M1 sequence contained a 1 base pair deletion in the 3' non-translated region, compared to the T1L and T3D M1 sequences. The T2J M1 gene showed ~80% nucleotide homology, and the encoded μ2 protein showed ~71% amino acid identity, with the T1L and T3D M1 and μ2 sequences, respectively, making the T2J M1 gene and μ2 proteins amongst the most divergent of all reovirus genes and proteins. Comparisons of these newly determined M1 and μ2 sequences with newly determined M1 and μ2 sequences from nine additional field isolates and a variety of laboratory T3D clones identified conserved features and/or regions that provide clues about μ2 structure and function.

Conclusions

The findings suggest a model for the domain organization of μ2 and provide further evidence for a role of μ2 in viral RNA synthesis. The new sequences were also used to explore the basis for M1/μ2-determined differences in the morphology of viral factories in infected cells. The findings confirm the key role of Ser/Pro208 as a prevalent determinant of differences in factory morphology among reovirus isolates and trace the divergence of this residue and its associated phenotype among the different laboratory-specific clones of type 3 Dearing.