Association of DRG1 and DRG2 with Ribosomes from Pea,Arabidopsis, and Yeast

Abstract

DRGs are highly conserved GTP binding proteins. All eukaryotes examined contain DRG1 and DRG2 orthologs. The first experimental evidence for GTP binding by a plant DRG1 protein and by DRG2 from any organism is presented. DRG1 antibodies recognized a single ;43-kDa band in plant tissues, whereas DRG2 antibodies recognized ;45-, 43-, and 30-kDa bands. An in vitro transcription and translation assay suggested that the 45-kDa band represents full-length DRG2 and that the smaller bands are specific proteolytic products. Homogenates from pea roots and root apices were used to produce fractions enriched in cytosolic and microsomal monosomes and polysomes. DRG1 and the 45-and 43-kDa DRG2 bands occurred in the cytosol and associated with cytosolic monosomes. In contrast, the 30-kDa form of DRG2 was strongly enriched in polysome fractions. Thus, DRG1 and the larger forms of DRG2 may be involved in translational initiation, and the 30-kDa form of DRG2 may be involved in translational elongation. DRG1 and the 45-and 43-kDa forms of DRG2 can reassociate with ribosomes in vitro, a process that is partially inhibited by GTP-g-S. Cells expressing FLAG-tagged ribosomal proteins from transgenic lines of Arabidopsis and yeast also demonstrated DRG-ribosome interactions.

The Jumonji-C oxygenase JMJD7 catalyzes (3S)-lysyl hydroxylation of TRAFAC GTPases

“…In addition to effects on protease hydrolysis, we observed JMJD7- and hydroxylation site-dependent regulation of RNA binding, analogous to the role of JMJD4 in promoting mRNA stop codon decoding by eRF114. Although future work is required to address the physiological RNA targets, the presence of DRGs in ribosome fractions from diverse species including yeasts, plants, and humans28,37,38 could be consistent with an interaction with messenger or ribosomal RNA. Although the biochemical role of the DRGs in protein translation is unclear, it is consistent with their similarity to other OBG GTPases of the TRAFAC family, which have roles in ribosome biogenesis and translation control23,39.…”

“…The discovery of JMJD7-catalyzed DRG hydroxylation contributes to growing evidence on the importance of the dynamic interactions between 2OG oxygenases and their substrates/interacting partners in disease6,41. Both JMJD7 and DRG1/DRG2 are linked to cell growth in diverse cell types and species29,37,42–44. JMJD7 and DRG1/2 may also have context dependent roles in diseases including cancer and mental disorders; the DRG2 gene is located in a chromosomal region implicated in the Smith-Magenis neurobehavioral syndrome45, and DRG1/2 SNPs have been identified in a screen of candidate genes for autism spectrum disorders46.…”

Human Drg1 is a potassium‐dependent GTPase enhanced by Lerepo4

“…Lerepo4 (or Dfrp1) was first identified in vitro and further confirmed in vivo as a partner of Drg1 [1,8,30], and it has been demonstrated in yeast to be responsible for its recruitment to polysomes [9,33]. Automated predictions have considered Lerepo4 as an intrinsically unstructured protein, and the structure of the C-terminal part of Tma46 solved in complex with Rbg1 corroborates this idea as it adopts a non-globular extended conformation, contacting the GTPase and TGS domains of Rbg1 [9].…”

“…It was first discovered as a developmentally regulated GTPase, abundantly transcribed in growing cells in mammalian and frog embryos and in actively growing tissues in plants , being predicted to regulate cell growth . It associates with polysomes, playing a role in translation .…”

“…Interestingly, although Drg1 is not essential, two and three highly similar paralog proteins can be found in animals and plants, respectively, suggesting an important role of these redundant proteins in fundamental biological processes . In this sense, microarray data and reporter gene assays have shown that DRGs from Arabidopsis thaliana are transcriptionally regulated, and the protein accumulates directly and specifically in response to heat stress and desiccation .…”