Disease relevance of replicase

• Nonsense mutations of replicase and movement protein genes contribute to the attenuation of an avirulent tomato mosaic virus [1].
• The replicase back mutant (ToMV-K(rase)) produced chlorosis and mosaic symptoms on N. tabacum cv. Huangmiaoyu (systemic host), while the MP recovery mutant (ToMV-K(mp)) produced no systemic symptoms on Huangmiaoyu tobacco [1].
• Changing patterns of localization of the tobacco mosaic virus movement protein and replicase to the endoplasmic reticulum and microtubules during infection [2].
• Transgenic tobacco (Nicotiana tabacum cv. Turkish Samsun NN) plants expressing a truncated replicase gene sequence from RNA-2 of strain Fny of cucumber mosaic virus (CMV) are resistant to systemic CMV disease [3].
• RNA helicase domain of tobamovirus replicase executes cell-to-cell movement possibly through collaboration with its nonconserved region [4].

High impact information on replicase

• Tobacco mosaic virus (TMV) derivatives that encode movement protein (MP) as a fusion to the green fluorescent protein (MP:GFP) were used in combination with antibody staining to identify host cell components to which MP and replicase accumulate in cells of infected Nicotiana benthamiana leaves and in infected BY-2 protoplasts [2].
• These results indicate that sequences complementary to the terminal 117 nucleotides of TMV, which include a putative replicase binding site, are responsible for the protection [5].
• In vitro mutagenesis of the putative replicase genes of tobacco mosaic virus [6].
• Analyses of recombinant viruses containing the L and L(11)A strains revealed that a single base change in the replicase gene, which causes an amino acid substitution, is responsible for the symptomless and suppressor-defective phenotypes of the attenuated strains [7].
• A protein-protein interaction within the helicase domain of the Tobacco mosaic virus (TMV) 126- and 183-kDa replicase proteins was previously implicated in virus replication (S. Goregaoker, D. Lewandowski, and J. Culver, Virology 282:320-328, 2001) [8].

Biological context of replicase

• The rescued phenotypes of the progeny viruses showed that the replicase and MP recovery mutant (ToMV-K(rase-mp)) induced severe symptoms on both systemic and necrotic plants similar to those induced by the virulent strain [1].
• The amino acid sequences of the shorter and longer (read through) RNA replicase components, movement protein (MP) and coat protein (CP) were 58, 58 [9].
• We have shown that virus-encoded replicase components of tobacco mosaic virus (TMV)(130K/180K proteins) could complement a replication-defective mutant (LDR28) for viral replication in trans [Ogawa et al. Virology 185, 580-584 (1991)] [10].
• The 1.4-kbp insertion in the replicase open reading frame (ORF) of the resistant plants was shown by DNA sequencing to be an IS10-like transposable element, which apparently inserted itself into the TMV sequence at nucleotide 2875 sometime during the propagation of this replicase ORF plasmid (pREP21) [11].
• Inserts of selected cDNA clones were sequenced to obtain the nucleotide sequence of the 126 K replicase component [12].

Anatomical context of replicase

• UR-hel, a chimeric virus obtained by replacement of the RNA helicase domain of tobacco mosaic virus (TMV)-U1 replicase with that from the TMV-R strain, could replicate similarly to TMV-U1 in protoplasts but could not move from cell to cell (K. Hirashima and Y. Watanabe, J. Virol. 75:8831-8836, 2001) [4].
• Selected B-cell epitopes were either inserted into the surface loop region of the TMV coat protein or fused to the C terminus using the leaky stop signal derived from the replicase protein reading frame [13].

Associations of replicase with chemical compounds

• All genomes had a statistically significant bias for G at every third (or 3n) position, resulting in a preponderance of GNN codons and hence a high Val, Ala, Gly, Asp, Glu content, at least in the large (126/183 kDa) and amino-coterminal replicase protein genes [14].

References