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PMID:21682783

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Citation

Lange, H, Sement, FM and Gagliardi, D (2011) MTR4, a putative RNA helicase and exosome co-factor, is required for proper rRNA biogenesis and development in Arabidopsis thaliana. Plant J. 68:51-63

Abstract

The exosome is a conserved protein complex that is responsible for essential 3'→5' RNA degradation in both the nucleus and the cytosol. It is composed of a nine-subunit core complex to which co-factors confer both RNA substrate recognition and ribonucleolytic activities. Very few exosome co-factors have been identified in plants. Here, we have characterized a putative RNA helicase, AtMTR4, that is involved in the degradation of several nucleolar exosome substrates in Arabidopsis thaliana. We show that AtMTR4, rather than its closely related protein HEN2, is required for proper rRNA biogenesis in Arabidopsis. AtMTR4 is mostly localized in the nucleolus, a subcellular compartmentalization that is shared with another exosome co-factor, RRP6L2. AtMTR4 and RRP6L2 cooperate in several steps of rRNA maturation and surveillance, such as processing the 5.8S rRNA and removal of rRNA maturation by-products. Interestingly, degradation of the Arabidopsis 5' external transcribed spacer (5' ETS) requires cooperation of both the 5'→3' and 3'→5' exoribonucleolytic pathways. Accumulating AtMTR4 targets give rise to illegitimate small RNAs; however, these do not affect rRNA metabolism or contribute to the phenotype of mtr4 mutants. Plants lacking AtMTR4 are viable but show several developmental defects, including aberrant vein patterning and pointed first leaves. The mtr4 phenotype resembles that of several ribosomal protein and nucleolin mutants, and may be explained by delayed ribosome biogenesis, as we observed a reduced rate of rRNA accumulation in mtr4 mutants. Taken together, these data link AtMTR4 with rRNA biogenesis and development in Arabidopsis.

Links

PubMed Online version:10.1111/j.1365-313X.2011.04675.x

Keywords


Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ARATH:MTR4

located_in

GO:0005634: nucleus

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

ARATH:MTR4

acts_upstream_of_or_within

GO:0031125: rRNA 3'-end processing

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:MTR4

acts_upstream_of_or_within

GO:0006364: rRNA processing

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:HEN2

located_in

GO:0005654: nucleoplasm

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete


See also

References

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