- Trans-splicing
Trans-splicing is an RNA processing event that fuses together sections of two different pre-mRNA sequences. In C. elegans, ~70% of mRNAs are trans-spliced to one of two 22 nucleotide spliced leaders, SL1 or SL2, with more than half of all transcripts undergoing SL1 splicing. During SL1 splicing, the 5' ends of pre-mRNAs are removed and replaced with SL1 sequence in a process very closely related to cis-splicing (intron/exon processing). SL1 sequence is ~100nt and is donated by small nuclear ribonucleoprotein particles (snRNPs). The remaining genes are trans-spliced by SL2. These genes are all downstream genes in closely spaced gene clusters similar to bacterial operons. They are transcribed from a promoter at the 5' end of the cluster of between 2 and 8 genes. This transcription makes a polycistronic pre-mRNA that is co-transcriptionally processed by cleavage and polyadenylation at the 3' end of each gene, and this event is closely coupled to the SL2 trans-splicing event that occurs only ~100 nt further downstream. Recent studies on the mechanism of SL2 trans-splicing have revealed that one of the 3' end formation proteins, CstF, interacts with the only protein known to be specific to the SL2 snRNP.
- RNA splicing
During pre-messenger RNA (pre-mrRNA) processing, cis-splicing reactions remove non-coding introns and joins coding exons. The majority of splicing is catalyzed by spliceosomes, large RNA-protein complexes composed of small nuclear ribonucleoproteins (snRNPs) that recognize splice donor and acceptor sites within the nascent RNA strand. Alternative mRNAs for a given gene can be created during the splicing reactions through varying the degree of cutting and splicing of introns and exons guided by alternative splice sites. C. elegans also exhibits trans-splicing where sequences from different primary RNA transcripts are used to make the mRNA. In C. elegans, ~70% of transcripts are trans-spliced with either a splice leader sequence SL1 or SL2 joined to the final transcript. Splice leaders are important
- Unfolded protein response - Cytosolic
A change in activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a protein that is not folded in its correct three-dimensional structure.
- Sensory perception
The series of events required for an organism to receive a sensory stimulus, convert it to a molecular signal, and recognize and characterize the signal. This is a neurological process.
- Signal transduction
Signal transduction begins with a stimulating event, such as a ligand binding to a receptor on the surface of the cell, and is followed by intracellular signaling steps that eventually trigger a response. In many cases the end response is modification of the regulation of gene transcription, but could also be the regulation of a metabolic process.
- Thermotaxis
The directed movement of an organism in response to a temperature gradient. Movement may be towards either a higher or lower temperature.
- Hormesis
The process whereby a low exposure to a toxin or stressor produces a generally positive response in the animal that is the opposite effect produced in response to a higher exposure. This can be observed in cases where C. elegans is exposed to short doses of temperature stress during development. Under such limited exposures, animals exhibit a longer life span than animals reared at room temperature. However, extended exposure to thermal stress results in severely shortened lifespans.
- Male sexual development
The establishment of the sex of a male organism by physical and physiological differentiation through sex-specific developmental pathways leading to a fully fertile male of the species.
- Adaptation
Adaptation occurs when a stimulus that once elicited a particular response, now elicits the opposite reaction. In C. elegans, this behavior has been shown through chemotaxis studies where extended exposure to an odor in the absence of food will result in a suppression of the chemotaxis response. In addition, by coupling an attractive stimulus to a starvation environment, the once attractive chemical is responded to as a repellent. However, these adaptations can be restored by brief exposure to the stimulus in the presence of food.