Toxoplasmosis is a parasitic disease caused by Toxoplasma gondii. Infections with toxoplasmosis usually cause no obvious symptoms in adults. Occasionally, people may have a few weeks or months of mild, flu-like illness such as muscle aches and tender lymph nodes. In a small number of people, eye problems may develop. In those with a weak immune system, severe symptoms such as seizures and poor coordination may occur. If infected during pregnancy, a condition known as congenital toxoplasmosis may affect the child.
Toxoplasma gondii is an obligate intracellular parasitic protozoan eukaryote that causes the infectious disease toxoplasmosis. Found worldwide, T. gondii is capable of infecting virtually all warm-blooded animals, but felids, such as domestic cats, are the only known definitive hosts in which the parasite may undergo sexual reproduction.
A regulatory sequence is a segment of a nucleic acid molecule which is capable of increasing or decreasing the expression of specific genes within an organism. Regulation of gene expression is an essential feature of all living organisms and viruses.
Tumor hypoxia is the situation where tumor cells have been deprived of oxygen. As a tumor grows, it rapidly outgrows its blood supply, leaving portions of the tumor with regions where the oxygen concentration is significantly lower than in healthy tissues. Hypoxic microenvironements in solid tumors are a result of available oxygen being consumed within 70 to 150 μm of tumour vasculature by rapidly proliferating tumor cells thus limiting the amount of oxygen available to diffuse further into the tumor tissue. In order to support continuous growth and proliferation in challenging hypoxic environments, cancer cells are found to alter their metabolism. Furthermore, hypoxia is known to change cell behavior and is associated with extracellular matrix remodeling and increased migratory and metastatic behavior.
The 5′ untranslated region is the region of an mRNA that is directly upstream from the initiation codon. This region is important for the regulation of translation of a transcript by differing mechanisms in viruses, prokaryotes and eukaryotes. While called untranslated, the 5′ UTR or a portion of it is sometimes translated into a protein product. This product can then regulate the translation of the main coding sequence of the mRNA. In many organisms, however, the 5′ UTR is completely untranslated, instead forming complex secondary structure to regulate translation.
Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida. As obligate intracellular parasites, they must live and reproduce within an animal cell. Coccidian parasites infect the intestinal tracts of animals, and are the largest group of apicomplexan protozoa.
The trp operon is an operon—a group of genes that is used, or transcribed, together—that codes for the components for production of tryptophan. The trp operon is present in many bacteria, but was first characterized in Escherichia coli. The operon is regulated so that, when tryptophan is present in the environment, the genes for tryptophan synthesis are not expressed. It was an important experimental system for learning about gene regulation, and is commonly used to teach gene regulation.
Amino acid synthesis is the set of biochemical processes by which the amino acids are produced. The substrates for these processes are various compounds in the organism's diet or growth media. Not all organisms are able to synthesize all amino acids. For example, humans can only synthesize 11 of the 20 standard amino acids, and in time of accelerated growth, histidine can be considered an essential amino acid.
In molecular biology lin-4 is a microRNA (miRNA) that was identified from a study of developmental timing in the nematode Caenorhabditis elegans. It was the first to be discovered of the miRNAs, a class of non-coding RNAs involved in gene regulation. miRNAs are transcribed as ~70 nucleotide precursors and subsequently processed by the Dicer enzyme to give a 21 nucleotide product. The extents of the hairpin precursors are not generally known and are estimated based on hairpin prediction. The products are thought to have regulatory roles through complete or partial complementarity to mRNA. The lin-4 gene has been found to lie within a 4.11kb intron of a separate host gene.
The mir-2 microRNA family includes the microRNA genes mir-2 and mir-13. Mir-2 is widespread in invertebrates, and it is the largest family of microRNAs in the model species Drosophila melanogaster. MicroRNAs from this family are produced from the 3' arm of the precursor hairpin. Leaman et al. showed that the miR-2 family regulates cell survival by translational repression of proapoptotic factors. Based on computational prediction of targets, a role in neural development and maintenance has been suggested.
The repression of heat shock gene expression (ROSE) element is an RNA element found in the 5' UTR of some heat shock protein's mRNAs. The ROSE element is an RNA thermometer that negatively regulates heat shock gene expression. The secondary structure is thought to be altered by temperature, thus it is an RNA thermometer. This structure blocks access to the ribosome binding site at normal temperatures. During heat shock however, the structure changes freeing the ribosome binding site and allowing expression to occur.
suhB, later renamed mmgR, was a putative non-coding RNA found multiple times in the Agrobacterium tumefaciens genome and related alpha-proteobacteria. Other non-coding RNAs uncovered in the same analysis include: speF, ybhL, metA, and serC.
Lactate dehydrogenase (LDH or LD) is an enzyme found in nearly all living cells. LDH catalyzes the conversion of lactate to pyruvate and back, as it converts NAD+ to NADH and back. A dehydrogenase is an enzyme that transfers a hydride from one molecule to another.
NrrF is a non-coding RNA which is regulated by the Ferric uptake regulator (Fur) protein in bacteria. This non-coding RNA was identified in Neisseria meningitidis and is involved in iron regulation of the succinate dehydrogenase genes sdhA and sdhC. NrrF acts as an antisense RNA and is complementary to the junction between the second and third genes of the sdh operon. Secondary structure predictions have indicated that this interaction occurs in a single stranded loop region of the NrrF RNA. Under low iron concentration NrrF is present at a high concentration and forms a duplex with the transcript in Hfq dependent manner. The RNA chaperone Hfq acts to enhance binding of NrrF or stabilizes the NrrF/sdh transcript duplex. Binding of NrrF results in down regulation of the sdhCDAB mRNA transcript results in a Fur-dependent positive regulation of succinate dehydrogenase. Another NrrF RNA target is mRNA petABC, coding for cytochrome bc1. Interaction between NrrF and the 5′ untranslated region of the petABC mRNA results in its repression.
Translational regulation refers to the control of the levels of protein synthesized from its mRNA. This regulation is vastly important to the cellular response to stressors, growth cues, and differentiation. In comparison to transcriptional regulation, it results in much more immediate cellular adjustment through direct regulation of protein concentration. The corresponding mechanisms are primarily targeted on the control of ribosome recruitment on the initiation codon, but can also involve modulation of peptide elongation, termination of protein synthesis, or ribosome biogenesis. While these general concepts are widely conserved, some of the finer details in this sort of regulation have been proven to differ between prokaryotic and eukaryotic organisms.
An RNA thermometer is a temperature-sensitive non-coding RNA molecule which regulates gene expression. RNA thermometers often regulate genes required during either a heat shock or cold shock response, but have been implicated in other regulatory roles such as in pathogenicity and starvation.
In molecular biology, the SAG1 protein domain is an example of a group of glycosylphosphatidylinositol (GPI)-linked proteins named SRSs. SAG1 is found on the surface of a protozoan parasite Toxoplasma gondii. This parasite infects almost any warm-blooded vertebrate. The surface of T. gondii is coated with a family of developmentally regulated glycosylphosphatidylinositol (GPI)-linked proteins (SRSs), of which SAG1 is the prototypic member.
In molecular biology mir-198 microRNA is a short RNA molecule. MicroRNAs function to regulate the expression levels of other genes by several mechanisms.
In molecular biology, the PyrC leader is a cis-regulatory RNA element found at the 5' of the PyrC mRNA in Enterobacteria. The PyrC gene encodes Dihydroorotase, an enzyme involved in pyrimidine biosynthesis. The PyrC leader regulates expression of PyrC. Translation initiation can occur at four different sites within this leader sequence, under high CTP conditions the translation initiation site is upstream of that used under low CTP conditions, additional cytosine residues are incorporated into the mRNA resulting in the formation of an RNA hairpin. This hairpin blocks ribosome-binding at the Shine-Dalgarno sequence, and therefore blocks expression of PyrC. Under low CTP conditions the initiation site is further downstream and does not result in hairpin formation, so the ribosome can bind to the Shine-Dalgarno sequence and PyrC is expressed.
In molecular biology, the PyrD leader is a cis-regulatory RNA element found at the 5' of the PyrC mRNA in Proteobacteria. The PyrD gene encodes dihydroorotate dehydrogenase, an enzyme involved in pyrimidine biosynthesis. The PyrD leader regulates expression of PyrD. Translation initiation can occur at more than one different site within this leader sequence, under high cytidine triphosphate or guanosine triphosphate conditions the translation initiation site is upstream of that used under low CTP/GTP conditions, additional cytosine residues are incorporated into the mRNA resulting in the formation of an RNA hairpin. This hairpin blocks ribosome-binding at the Shine-Dalgarno sequence, and therefore blocks expression of PyrD. Under low CTP/GTP conditions the initiation site is further downstream and does not result in hairpin formation, so the ribosome can bind to the Shine-Dalgarno sequence and PyrD is expressed.
