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Reversion of the Arabidopsis rpn12a-1 exon-trap mutation by an intragenic suppressor that weakens the chimeric 5' splice site.
MedLine Citation:
PMID:  24358894     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: In the Arabidopsis 26S proteasome mutant rpn12a-1, an exon-trap T-DNA is inserted 531 base pairs downstream of the RPN12a STOP codon. We have previously shown that this insertion activates a STOP codon-associated latent 5' splice site that competes with the polyadenylation signal during processing of the pre-mRNA. As a result of this dual input from splicing and polyadenylation in the rpn12a-1 mutant, two RPN12a transcripts are produced and they encode the wild-type RPN12a and a chimeric RPN12a-NPTII protein. Both proteins form complexes with other proteasome subunits leading to the formation of wild-type and mutant proteasome versions. The net result of this heterogeneity of proteasome particles is a reduction of total cellular proteasome activity. One of the consequences of reduced proteasomal activity is decreased sensitivity to the major plant hormone cytokinin.
METHODS: We performed ethyl methanesulfonate mutagenesis of rpn12a-1 and isolated revertants with wild-type cytokinin sensitivity.
RESULTS: We describe the isolation and analyses of suppressor of rpn12a-1 ( sor1). The sor1 mutation is intragenic and located at the fifth position of the chimeric intron. This mutation weakens the activated 5' splice site associated with the STOP codon and tilts the processing of the RPN12a mRNA back towards polyadenylation.
CONCLUSIONS: These results validate our earlier interpretation of the unusual nature of the rpn12a-1 mutation. Furthermore, the data show that optimal 26S proteasome activity requires RPN12a accumulation beyond a critical threshold. Finally, this finding reinforces our previous conclusion that proteasome function is critical for the cytokinin-dependent regulation of plant growth.
Authors:
Jasmina Kurepa; Yan Li; Jan A Smalle
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Publication Detail:
Type:  Journal Article     Date:  2013-02-25
Journal Detail:
Title:  F1000Research     Volume:  2     ISSN:  2046-1402     ISO Abbreviation:  F1000Res     Publication Date:  2013  
Date Detail:
Created Date:  2014-02-20     Completed Date:  2014-02-20     Revised Date:  2014-07-31    
Medline Journal Info:
Nlm Unique ID:  101594320     Medline TA:  F1000Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  60     Citation Subset:  -    
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