Crystal structures of two archaeal Pelotas reveal inter-domain structural plasticity

Dom34 from Saccharomyces cerevisiae is one of the key players in no-go mRNA decay, a surveillance pathway by which an abnormal mRNA stalled during translation is degraded by an endonucleolytic cleavage. Its homologs called Pelota are found in other species. We showed previously that S. cerevisiae Dom34 (domain 1) has an endoribonuclease activity, which suggests its direct catalytic role in no-go decay. Pelota from Thermoplasma acidophilum and Dom34 from S. cerevisiae have been structurally characterized, revealing a tripartite architecture with a significant difference in their overall conformations. To gain further insights into structural plasticity of the Pelota proteins, we have determined the crystal structures of two archaeal Pelotas from Archaeoglobus fulgidus and Sulfolobus solfataricus. Despite the structural similarity of their individual domains to those of T. acidophilum Pelota and S. cerevisiae Dom34, their overall conformations are distinct from those of T. acidophilum Pelota and S. cerevisiae Dom34. Different overall conformations are due to conformational flexibility of the two linker regions between domains 1 and 2 and between domains 2 and 3. The observed inter-domain structural plasticity of Pelota proteins suggests that large conformational changes are essential for their functions.     

An Arabidopsis homologue of the Drosophila meiotic gene Pelota

We have identified a plant homologue of the Drosophila meiotic gene Pelota in Arabidopsis thaliana (AtPelota1). This gene maps to chromosome 4 of Ara- bidopsis and is one of two Pelota homologues present in this plant. When the expression pattern of AtPelota1 was examined it was found to be expressed at similar levels in all plant tissues tested (whole plant, bud, stem, leaf and root). This expression pattern corresponds to that seen for some other Arabidopsis meiotic genes and their homologues. A search of the databases reveal that the AtPelota gene family is widespread with homologues present in higher and lower eukaryotes and archaebacteria, but not eubacteria. Received: 13 December 1999 / Accepted: 27 December 1999     

Dissociation by Pelota, Hbs1 and ABCE1 of mammalian vacant 80S ribosomes and stalled elongation complexes

No-go decay (NGD) and non-stop decay (NSD) are eukaryotic surveillance mechanisms that target mRNAs on which elongation complexes (ECs) are stalled by, for example, stable secondary structures (NGD) or due to the absence of a stop codon (NSD). Two interacting proteins Dom34(yeast)/Pelota(mammals) and Hbs1, which are paralogues of eRF1 and eRF3, are implicated in these processes. Dom34/Hbs1 were shown to promote dissociation of stalled ECs and release of intact peptidyl-tRNA. Using an in vitro reconstitution approach, we investigated the activities of mammalian Pelota/Hbs1 and report that Pelota/Hbs1 also induced dissociation of ECs and release of peptidyl-tRNA, but only in the presence of ABCE1. Whereas Pelota and ABCE1 were essential, Hbs1 had a stimulatory effect. Importantly, ABCE1/Pelota/Hbs1 dissociated ECs containing only a limited number of mRNA nucleotides downstream of the P-site, which suggests that ABCE1/Pelota/Hbs1 would disassemble NSD complexes stalled at the 3'-end, but not pre-cleavage NGD complexes stalled in the middle of mRNA. ABCE1/Pelota/Hbs1 also dissociated vacant 80S ribosomes, which stimulated 48S complex formation, suggesting that Pelota/Hbs1 have an additional role outside of NGD.     

An archaebacterial homolog of pelota, a meiotic cell division protein in eukaryotes

Abstract An open reading frame ( pelA ) specifying a homolog of pelota and DOM34, proteins required for meiotic cell division in Drosophila melanogaster and Saccharomyces cerevisiae , respectively, has been cloned, sequenced and identified from the archaebacterium Sulfolobus solfataricus . The S. solfataricus PelA protein is about 20% identical with pelota, DOM34 and the hypothetical protein R74.6 of Caenorhabditis elegans . The presence of a pelota homolog in archaebacteria implies that the meiotic functions of the eukaryotic protein were co-opted from, or added to, other functions existing before the emergence of eukaryotes. The nuclear localization signal and negatively charged carboxy-terminus characteristic of eukaryotic pelota-like proteins are absent from the S. solfataricus homolog, and hence may be indicative of the acquired eukaryotic function(s).     

RNA degradation is required for the germ-cell to maternal transition in Drosophila

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