A mitochondrial rRNA dimethyladenosine methyltransferase in Arabidopsis.

Institut für Biologie/Genetik, Humboldt-Universität, Chausseestr. 117, 10115 Berlin, Germany.
The Plant Journal (Impact Factor: 6.82). 11/2009; 61(4):558-69. DOI: 10.1111/j.1365-313X.2009.04079.x
Source: PubMed

ABSTRACT S-adenosyl-L-methionine-dependent rRNA dimethylases mediate the methylation of two conserved adenosines near the 3' end of the rRNA in the small ribosomal subunits of bacteria, archaea and eukaryotes. Proteins related to this family of dimethylases play an essential role as transcription factors (mtTFBs) in fungal and animal mitochondria. Human mitochondrial rRNA is methylated and human mitochondria contain two related mtTFBs, one proposed to act as rRNA dimethylase, the other as transcription factor. The nuclear genome of Arabidopsis thaliana encodes three dimethylase/mtTFB-like proteins, one of which, Dim1B, is shown here to be imported into mitochondria. Transcription initiation by mitochondrial RNA polymerases appears not to be stimulated by Dim1B in vitro. In line with this finding, phylogenetic analyses revealed Dim1B to be more closely related to a group of eukaryotic non-mitochondrial rRNA dimethylases (Dim1s) than to fungal and animal mtTFBs. We found that Dim1B was capable of substituting the E. coli rRNA dimethylase activity of KsgA. Moreover, we observed methylation of the conserved adenines in the 18S rRNA of Arabidopsis mitochondria; this modification was not detectable in a mutant lacking Dim1B. These data provide evidence: (i) for rRNA methylation in Arabidopsis mitochondria; and (ii) that Dim1B is the enzyme catalyzing this process.

  • [Show abstract] [Hide abstract]
    ABSTRACT: We constructed a skin cDNA library of the Liaoning cashmere goat during follicle anagen. The recombination was over 89%. A total of 1,986 expressed sequence tags (ESTs) were sequenced. After assembly, 1,126 ESTs that were homologous to functionally characterized or hypothetical proteins were obtained. BLASTX searches found 904 ESTs that had strong matches to known proteins. More than 50% of the ESTs were similar to proteins that were annotated either as related to enzyme/catalytic activity (26.5%) or as being involved in cell activities, such as growth differentiation, proliferation, apoptosis, transportation, and signal transmission (25.9%). 1.2% of the ESTs were similar to proteins that were related to hair/hair follicle. By analyzing the structure of the unisequences, 81 full-length cDNA clones were identified, none of which had yet been identified in goat. We selected two full-length cDNA clones with predicted proteins, which were similar to dimethyladenosine transferase 1-like (DIMT1L) and coatomer protein complex, subunit zeta (ζ-COP). An analysis of the tertiary structure of the DIMT1L homolog showed that it had a methyltransferase domain. The ζ-COP was a short chain and had a simple tertiary structure. In order to study DIMT1L and ζ-COP genes expression, the semi-quantitative RT–PCR was used to detect whether DIMT1L and ζ-COP genes were expressed in heart, liver, spleen, lung, kidney tissues and in situ hybridization (ISH) to detect DIMT1L and ζ-COP genes expression location. Both DIMT1L and ζ-COP genes had high expression levels in heart and skin, and low levels in liver, kidney, lung and spleen. Moreover, DIMT1L and ζ-COP genes had a strong expression in the inner root sheath of the primary hair follicles (PF) and the secondary hair follicles (SF). The ζ-COP gene also had a strong expression in the surrounding tissue. In conclusion, we have successfully constructed a skin cDNA library from Liaoning cashmere goat during follicle anagen and characterized two genes. The cDNA library could become a valuable source to study the biology genetic characteristics of Liaoning cashmere goat and may provide an important platform for protecting genomic resources and improving the breed.
    Livestock Science 06/2014; 164. DOI:10.1016/j.livsci.2014.02.019 · 1.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Plastid genes are transcribed by two types of RNA polymerase in angiosperms: the bacterial type plastid-encoded RNA polymerase (PEP) and one (RPOTp in monocots) or two (RPOTp and RPOTmp in dicots) nuclear-encoded RNA polymerase(s) (NEP). PEP is a bacterial-type multisubunit enzyme composed of core subunits (coded for by the plastid rpoA, rpoB, rpoC1 and rpoC2 genes) and additional protein factors (sigma factors and polymerase associated protein, PAPs) encoded in the nuclear genome. Sigma factors are required by PEP for promoter recognition. Six different sigma factors are used by PEP in Arabidopsis plastids. NEP activity is represented by phage-type RNA polymerases. Only one NEP subunit has been identified, which bears the catalytic activity. NEP and PEP use different promoters. Many plastid genes have both PEP and NEP promoters. PEP dominates in the transcription of photosynthesis genes. Intriguingly, rpoB belongs to the few genes transcribed exclusively by NEP. Both NEP and PEP are active in non-green plastids and in chloroplasts at all stages of development. The transcriptional activity of NEP and PEP is affected by endogenous and exogenous factors. This article is part of a Special Issue entitled: Chloroplast Biogenesis.
    Biochimica et Biophysica Acta (BBA) - Bioenergetics 02/2015; DOI:10.1016/j.bbabio.2015.02.004 · 4.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The mitochondrial DNA mutation m.1555A>G predisposes to hearing loss following aminoglycoside antibiotic exposure in an idiosyncratic dose-independent manner. However, it may also cause maternally inherited hearing loss in the absence of aminoglycoside exposure or any other clinical features (non-syndromic hearing loss). Although m.1555A>G was identified as a cause of deafness more than twenty years ago, the pathogenic mechanism of this mutation of ribosomal RNA remains controversial. Different mechanistic concepts have been proposed. Most recently, evidence from cell lines and animal models suggested that patients with m.1555A>G may have more 12S rRNA m(6) 2A methylation than controls, so called 'hypermethylation'. This has been implicated as a pathogenic mechanism of mitochondrial dysfunction but has yet to be validated in patients. 12S m(6) 2A rRNA methylation, by the TFB1M enzyme, occurs at two successive nucleotides (m.1584A and m.1583A) in close proximity to m.1555A>G. We examined m(6) 2A methylation in 14 patients with m.1555A>G, and controls, and found all detectable 12S rRNA transcripts to be methylated in both groups. Moreover, different RNA samples derived from the same patient (lymphocyte, fibroblast and lymphoblast) revealed that only transformed cells contained some unmethylated 12S rRNA transcripts, with all detectable 12S rRNA transcripts derived from primary samples m(6) 2A methylated. Our data indicate that TFB1M 12S m(6) 2A rRNA hypermethylation is unlikely to be a pathogenic mechanism and may be an artefact of previous experimental models studied. We propose that RNA methylation studies in experimental models should be validated in primary clinical samples to ensure that they are applicable to the human situation.
    Human Molecular Genetics 10/2014; 24(4). DOI:10.1093/hmg/ddu518 · 6.68 Impact Factor

Full-text (2 Sources)

Available from
Oct 16, 2014