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Repressible systems - A repressible system is on except in the presence of some molecule (called a corepressor) that suppresses gene expression. The molecule is said to "repress expression". The manner by which this happens is dependent on the control mechanisms as well as differences between prokaryotic and eukaryotic cells.
In prokaryotes, the term corepressor is used to denote the activating ligand of a repressor protein. For example, the E. coli tryptophan repressor (TrpR) is only able to bind to DNA and repress transcription of the trp operon when its corepressor tryptophan is bound to it.
An adaptive enzyme or inducible enzyme is an enzyme that is expressed only under conditions in which it is clearly of adaptive value, as opposed to a constitutive enzyme which is produced all the time. [1] [2] The inducible enzyme is used for the breaking-down of things in the cell.
Endogenously expressed miRNA in metazoans is usually not perfectly complementary to a large number of genes and thus, they modulate expression via translational repression. [ 51 ] [ 52 ] However, in plants , the process has a much greater specificity to target mRNA and usually each miRNA only binds to one mRNA.
The L-arabinose operon houses genes coding for arabinose-digesting enzymes. These function to break down arabinose as an alternative source for energy when glucose is low or absent. [ 4 ] The operon consists of a regulatory repressor gene (araC), three control sites (ara02, ara01, araI1, and araI2), two promoters (Parac/ParaBAD) and three ...
Several cell function specific transcription factor proteins (in 2018 Lambert et al. indicated there were about 1,600 transcription factors in a human cell [41]) generally bind to specific motifs on an enhancer [22] and a small combination of these enhancer-bound transcription factors, when brought close to a promoter by a DNA loop, govern the ...
Transcription start sites of housekeeping genes can span over a region of around 100 bp whereas transcription start sites of developmentally regulated genes are usually focused in a narrow region. [ 9 ] [ 10 ] [ 11 ] Little is known about how the dispersed transcription initiation of housekeeping gene is established.
After being produced, the stability and distribution of the different transcripts is regulated (post-transcriptional regulation) by means of RNA binding protein (RBP) that control the various steps and rates controlling events such as alternative splicing, nuclear degradation (), processing, nuclear export (three alternative pathways), sequestration in P-bodies for storage or degradation and ...