Functional modulation of the geminivirus AL2 transcription factor and silencing suppressor by self-interaction.
J Virol
; 81(21): 11972-81, 2007 Nov.
Article
em En
| MEDLINE
| ID: mdl-17715241
ABSTRACT
The DNA genomes of geminiviruses have a limited coding capacity that is compensated for by the production of small multifunctional proteins. The AL2 protein encoded by members of the genus Begomovirus (e.g., Tomato golden mosaic virus) is a transcriptional activator, a silencing suppressor, and a suppressor of a basal defense. The related L2 protein of Beet curly top virus (genus Curtovirus) shares the pathogenicity functions of AL2 but lacks transcriptional activation activity. It is known that AL2 and L2 can suppress local silencing by interacting with adenosine kinase (ADK) and can suppress basal defense by interacting with SNF1 kinase. However, how the activities of these viral proteins are regulated remains an unanswered question. Here, we provide some answers by demonstrating that AL2, but not L2, interacts with itself. The zinc finger-like motif (CCHC) is required but is not sufficient for AL2 self-interaction. Alanine substitutions for the invariant cysteine residues that comprise the motif abolish self-interaction or cause aberrant subnuclear localization but do not abolish interaction with ADK and SNF1. Using bimolecular fluorescence complementation, we show that AL2AL2 complexes accumulate primarily in the nucleus, whereas AL2ADK and L2ADK complexes accumulate mainly in the cytoplasm. Further, the cysteine residue mutations impair the ability of AL2 to activate the coat protein promoter but do not affect local silencing suppression. Thus, AL2 self-interaction correlates with nuclear localization and efficient activation of transcription, whereas AL2 and L2 monomers can suppress local silencing by interacting with ADK in the cytoplasm.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Proteínas Virais
/
Transativadores
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Geminiviridae
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
2007
Tipo de documento:
Article