More than half of the recognized genera of positive strand RNA viruses
employ polyprotein processing as one of the strategies for their genome expression.
Normally, this processing is mediated by virus-encoded proteinases that belong to
the trypsin-like or papain-like family. In particular, papain-like, leader proteinases
were found in diverse families of human, animal, plant, and fungal positive strand
RNA viruses. In addition to autocatalytic processing, these proteinases play a
variety of roles in the virus life cycle. In plant potyviruses, a papain-like helper
component-proteinase (HC-Pro) was implicated in genome amplification, cell-to-cell
movement, long distance transport, and suppression of host defense. The p29
proteinase encoded by a fungal hypovirus CHV1 was found to be dispensable for
virus replication, but it was identified as a major determinant of viral pathogenicity.
In an animal equine aterivirus (EAV), a papain-like proteinase nspl was
demonstrated to possess a putative zinc finger domain, which functions in
subgenomic RNA synthesis, although it is not essential for virus replication. The
Lab proteinase of the foot and mouse disease virus (FMDV) is involved in
inhibition of cellular mRNA translation and in virus spread in infected animals. In
general, it appears that functional plasticity of the papain-like leader proteinases
played an important role in the evolution of viral diversity.
Here, we examined the functions of a papain-like leader proteinase (L-Pro)
in the life cycle of the beet yellows closterovirus (BYV). It was found that L-Pro is
required for autoproteolytic processing, genome amplification, virus invasiveness
and cell-to-cell movement for BYV. The gene swapping experiments involving
several closterviruses, a potyvirus, as well as CHV1, FMDV, and EAV revealed
complex functional profiles of the papain-like leader proteinases. The possible
mechanisms that underlie L-Pro functions are discussed. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32458 |
| Date | 04 April 2002 |
| Creators | Peng, Chih-Wen |
| Contributors | Dolja, Valerian V. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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