Together, these mechanisms are known as attenuation and antitermination, and both involve controlling the formation of a transcription. Some antitermination factors allow bypass of a single terminator in response to a . Attenuation through ribosome positioning, Leader RNA, Typical of amino. This mechanism is very similar to attenuation, but antitermination can be distinguished RNA-Binding Protein-Mediated Antitermination: The Sac/Bgl Family of.
|Published (Last):||11 December 2005|
|PDF File Size:||17.56 Mb|
|ePub File Size:||17.74 Mb|
|Price:||Free* [*Free Regsitration Required]|
It stimulates the rate of transcription elongation and is required for the activity of certain Rho-dependent terminators.
Protection of antiterminator RNA by the transcript elongation complex. These proteins prevent formation of Rho-independent transcription terminators in the nascent mRNA upstream of the regulated gene s 3. Antitermination by a stalled ribosome In most Gram-negative bacteria, the ribosome controls expression of amino acid biosynthesis operons in response to the availability of the cognate amino acid by sensing the level of charged tRNA Interaction surface of the transcription terminator Rho required to form a complex with the C-terminal domain of the antiterminator NusG.
Phage HK t L and t R.
Antitermination Control of Gene Expression (Molecular Biology)
By contrast, regulators from the second class modify RNAP into a processive, pause- and terminator-resistant state. Phages that are related to lambda have different N genes and different antitermination specificities.
As the mechanism of switching is conceptually the same whether a terminator or an antiterminator is favoured, other riboswitches that activate expression are likely to exist. Antitermination is the prokaryotic cell’s aid to fix premature termination of RNA synthesis during the transcription of RNA.
RNA remodeling and gene regulation by cold shock proteins. Adenine riboswitches and gene activation by disruption of a transcription terminator. NusG acts in concert with Rho to inhibit the expression of foreign genes 22whereas RfaH inhibits Rho action and, thus, activates expression of laterally acquired genes The mechanism of intrinsic transcription termination. To understand termination and its control by accessory factors, we must now probe the structure and dynamics of termination intermediates in real time.
Like BglG in E. Peters JM, et al.
Antitermination – Wikipedia
By stabilizing the clamp, a regulator could favour the active, catalytically competent state of the elongation complex. From this intermediate, RNAP can either escape upon addition of another nucleotide or isomerize into a termination complex. RNA polymerase interacts with transcription units in such a way that an ancillary factor can sponsor antitermination specifically for some transcripts.
This regulatory system couples the availability of the inducer, glucose, to the phosphorylation state of the antiterminator: Rabhi M, et al. Some of these signals serve as checkpoints of gene expression; for example, a pause may mediate recruitment of a regulatory factor to the RNAP 45 or provide sufficient time for the ribosome to initiate translation 6.
Termination factor for RNA synthesis. Binding of HutP disrupts the terminator and allows expression of the hut genes In addition to the antitermination mechanism described above, processing of the leader RNA has been shown to play a role in regulating expression of the B.
Riboswitches encode various regulatory elements: The publisher’s final antiterminatjon version of this article is available at Nat Rev Microbiol.
Ribosomal protein S4 is a transcription factor with properties remarkably similar to NusA, a protein involved in both non-ribosomal and ribosomal RNA antitermination. Rho-independent transcription terminators exist in leader regions upstream of both sacPA and sacB and prevent transcription of the structural genes in the absence of the inducer, which is sucrose.
Aminoacylation of this tRNA is predicted to interfere with the interaction at the CCA end and prevent the charged tRNA from binding; the leader transcript then folds into the conformation with the terminator, halting transcription. Like lambda N and Q, the PUT sequences suppress polymerase pausing and promote processive antitermination in a purified in vitro transcription system.
It is believed that this accounts for the phage specificity of N-mediated antitermination. Werner F, Antktermination D. Phage and bacterial antiterminators differ in several respects: We argue that the stable in vivo association of RfaH with the elongation complex 91 requires sequestration of the RfaH C-terminal domain, probably by the ribosome.