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Core protein mu2 is a second determinant of nucleoside triphosphatase activities by reovirus cores
1Institute for Molecular Virology, Graduate School, and Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, 52706, USA.
Abstract:
NTPase activities in mammalian reovirus cores were examined under various conditions that permitted several new differences to be identified between strains type 1 Lang (T1L) and type 3 Dearing (T3D). One difference concerned the ratio (at pH 8.5) of ATP hydrolysis at 50 degrees C to that at 35 degrees C. A genetic analysis using T1L x T3D reassortant viruses implicated the L3 and M1 gene segments in this difference, with M1 influencing ATPase activity most strongly at high temperatures. L3 and M1 encode the core proteins lambda1 and mu2, respectively. Another difference concerned the absolute levels of GTP hydrolysis by cores at 45 degrees C and pH 6.5. A genetic analysis using T1L x T3D reassortants implicated the M1 gene as the sole determinant of this difference. The results of these experiments, coupled with previous findings (S. Noble and M. L. Nibert, J. Virol. 71:2182-2191, 1997), suggest either that a single type of NTPase in cores is strongly influenced by two different core proteins--lambda1 and mu2--or that cores contain two different types of NTPase influenced by the two proteins. The findings appear relevant for understanding the complex functions of reovirus cores in RNA synthesis and capping.
Insights
Mammalian reovirus cores exhibit distinct nucleotide hydrolysis (NTPase) activities between strains. Genetic analysis reveals core proteins lambda1 and mu2, encoded by L3 and M1 gene segments, influence these differences.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Mammalian reoviruses possess core structures with essential enzymatic functions.
- Understanding reovirus core NTPase activities is crucial for deciphering viral RNA synthesis and capping mechanisms.
Purpose of the Study:
- To identify and characterize strain-specific differences in nucleotide hydrolysis (NTPase) activities between mammalian reovirus types 1 Lang (T1L) and 3 Dearing (T3D).
- To elucidate the genetic basis of observed NTPase activity variations, specifically implicating core proteins and their encoding gene segments.
Main Methods:
- Comparative analysis of ATP and GTP hydrolysis rates in reovirus cores under varying temperature and pH conditions.
- Genetic analysis using reassortant viruses derived from T1L and T3D strains to map gene segments responsible for NTPase differences.
- Correlation of genetic findings with the known functions of reovirus core proteins lambda1 (L3 gene) and mu2 (M1 gene).
Main Results:
- Significant differences in the ratio of ATP hydrolysis at high versus low temperatures (50°C vs. 35°C at pH 8.5) were observed between T1L and T3D reovirus cores.
- The M1 gene segment, encoding the mu2 core protein, was identified as a key determinant influencing ATPase activity, particularly at elevated temperatures.
- Differences in the absolute levels of GTP hydrolysis (at 45°C and pH 6.5) were solely attributed to the M1 gene segment.
- Genetic analysis implicated both L3 (lambda1) and M1 (mu2) gene segments in temperature-dependent ATPase activity, with M1 showing a stronger influence at high temperatures.
Conclusions:
- The findings suggest either a single reovirus core NTPase is modulated by both lambda1 and mu2 proteins, or two distinct NTPases exist, each influenced by one of these proteins.
- These results provide critical insights into the complex roles of reovirus core proteins in viral RNA metabolism and replication.
- The identified genetic determinants of NTPase activity are vital for understanding reovirus pathogenesis and for developing potential antiviral strategies.