Proteolytic cleavage analysis at the Murray Valley encephalitis virus NS1-2A junction

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Addis, Siti Nor Khadijah
Lee, Eva
Bettadapura, Jayaram
Lobigs, Mario
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2015
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Abstract

Background: Our understanding of the proteolytic processing events at the NS1-2A junction in the flavivirus polyprotein has not markedly progressed since the early work conducted on dengue virus (DENV). This work identified an octapeptide sequence located immediately upstream of the cleavage site thought to be important in substrate recognition by an as yet unknown, endoplasmic reticulum-resident host protease. Of the eight amino acid recognition sequence, the highly conserved residues at positions P1, P3, P5, P7 and P8 (with respect to N-terminus of NS2A) are particularly sensitive to amino acid substitutions in terms of DENV NS1-NS2A cleavage efficiency; however, the role of the octapeptide in efficient NS1 and NS2A production of other flaviviruses has not been experimentally addressed.

Methods and Results: Using site-directed mutagenesis at the NS1-2A cleavage site of Murray Valley encephalitis virus (MVEV), we confirmed the dominant role of conserved octapeptide residues for efficient NS1-2A cleavage, while changes at variable and the P1’ residues were mostly tolerated. However, digressions from the consensus cleavage motif derived from studies on DENV were also found. Thus, comparison of the impact on cleavage of mutations at the NS1-2A junction of MVEV and DENV showed virus-specific differences at both conserved and variable residues.

Conclusion: We show, with subgenomic expression and infectious clone-derived mutants of MVEV that conserved residues in the flavivirus octapeptide motif can be replaced with a different amino acid without markedly reducing cleavage efficiency of NS1 and NS2A.

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Virology Journal

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12

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1

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© 2015 Addis et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Page numbers are not for citation purposes. Instead, this article has the unique article number of 144.

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Microbiology not elsewhere classified

Microbiology

Medical Microbiology

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