EGO-1 is related to RNA-directed RNA polymerase and functions in germ-line development and RNA interference in C. elegans

Abstract

The ego-1 gene is the first example of a gene encoding an RdRP-related protein with an essential developmental function. The ego-1 gene is also required for a robust response to RNA interference by certain genes. Hence, a protein required for germ-line development in C. elegans may be a component of the RNA interference/PTGS machinery.

The four Rs of RNA-directed evolution

“…In Neurospora crassa 18,19 , plants 20 , Schizosaccharomyces pombe 21 and Caenorhabditis elegans 22 , but not in flies, humans or mouse oocyctes 18,19,23,24 , PTGS can also be initiated by an RNA-dependent RNA polymerase (RdRP) that synthesizes complementary RNA from highly expressed transcripts to generate dsRNA. This process can spread from the 3´ to the 5´ end of the mRNA, leading to progressive silencing of a gene and other mRNAs with exons in common (transitive RNAi) 18,22 .…”

“…This process can spread from the 3´ to the 5´ end of the mRNA, leading to progressive silencing of a gene and other mRNAs with exons in common (transitive RNAi) 18,22 . From the evolutionary viewpoint, transitive RNAi favors the generation of new phenotypes, as related genes in species with polyploid genomes will escape cosuppression by sequence divergence, resulting in altered function or expression.…”

Antiviral responses of arthropod vectors: an update on recent advances

“…Systemic RNAi and amplification of small RNAs has been shown in plants and Caenorhabditis elegans [113,124,131]. In D. melanogaster it has been shown that systemic spread of the RNAi response is essential for an efficient antiviral response and components of the dsRNA uptake machinery have been identified [60,98].…”

Gene silencing: Double-stranded RNA mediated mRNA degradation and gene inactivation

“…Aberrant RNAs that are misspliced and polyadenylated irregularly have been detected in a chalcone synthase PTGS system in petunia [37]. A new aspect of ego1 C. elegans Smardon et al 2000 [12] eIF2C-like qde2 Neurospora Catalanotto et al 2000 [42] Rde1 C. elegans Tabara et al 1999 [43] ago1 Arabidopsis Fagard et al 2000 [20] RecQ DNA qde3 Neurospora Cogoni et al 1999 [44] RNase D-like mut-7 C. elegans Ketting et al 1999 [45] RNA helicase mut-6 Chlamydomonas Wu-Scharf et al 2000 [33] Coiled-coil Protein Sgs3 Arabidopsis Mourrain et al 2000 [21] NMD Proteins smg2,5,6 C. elegans Domeier et al 2000 [46] rgs-CaM No Nicotiana tabacum Domeier et al 2000 [46] ago1 argonaute1; ego1, enhancer of glp-1; qde, quelling defective; rde, RNA interference deficient; rgr-CaM, regulator of gene silencing calmodulin-like protein; sde, silencing defective; sgs, suppressor of gene silencing silencing processes is the possible link with nonsense-mediated decay (NMD), an evolutionarily conserved pathway in which mRNAs that contain a premature stop codon are selectively degraded. Antisense constructs probably also produce RNAs that feed into the dsRNA-induced degradation pathway [38], [39].…”

“…The common features of these models include: 1) The synthesis and amplification of dsRNA; 2) Unwinding of dsRNA; and 3) Targeting of mRNAs after binding to the ribosome. The cellular RNA-directed RNA polymerase (RdRP) plays a central role in PTGS and is required where the process is induced directly by exogenously supplied dsRNA [12]. In Arabidopsis, RdRP is required for transgene-induced PTGS where one possible function is the synthesis of cRNA from aberrant RNA templates, leading to the formation of dsRNA (Fig 1).…”