Team:DTU-Denmark/Basics

The RNA Polymerase (RNAP)

In synthetic biology when creating the minimal cell XXX factors have been identified as essential for normal function of RNAP, both regarding normal elongation but also in terms of normal termination function. (REFFF) of these XXX have been identified to take part in regulatory function. While the rest is core subunits. Of interest for regulation in terms of termination Anti-termination will be highlighted:

• NusA:
• NusG:
• NusE:
• NusB:

Due to the construction of the RNAP of many subcomponents and systems, the function of the RNAP can be regulated by only adding or changing one or a few factors. This is the mechanism in the different termination and anti-termination functions described below.

Figure and table containing normal transcription and normal termination and table with sub-part names and explanation.

Termination

(terminator introduction)

Termination can fall into one of two categories:

• Intrinsic Termination
• Factor-dependent Termination

Intrinsic Termination

Intrinsic Termination can be found to occur at defined template sequences, usually a region of hyphenated inverted sequence symmetry followed by a run of T residues. Termination through intrinsic terminators is stimulated by additional factors, e.g. NusA. Termination occurs due to the stem-loop structure formed by the base-pairing of mRNA with itself caused by inverted sequence symmetry, followed by the run of T residues. The NusA protein causes the RNA-p complex to temporarily stall at the stem-loop structure, when this is followed by a poly-A tail, the RNA-DNA duplex is destabilized. This causes the RNA-p to dissociate from the DNA, thereby terminating transcription. Termination function step-by-step.

Factor dependent Termination

Factor-dependent Termination occurs due to events that are not directly related to transcription, such as the release of ribosomes from nascent transcript or DNA damage. One such host termination factor is Rho, which acts on many sites along the bacterial chromosome. (( ??MFD, is a host termination factor that is responsible for releasing RNA-p stalled at sites of UV-induced DNA lesions. ??)) rho-dependent termination is characterized by not having a specific hairpin structure involved in the termination. The termination thus happens whendue to XXXXXX, and what have been found of the termination site any commen sequences or consensus ????????????????? the function of rho dependent termination, have been shown to be affected by XXXX. The rho binding sites on the mRNA, have been identified from XXbp to XXXbp of stream of the termination site. Rho-termination is thus an example of the more complex termination regulation that is not fully understood and can be very difficult to define and use for engineering purposes. Thus for a more defined anti-termination system the lambda N-protein system and the interaction with the nut-site in the phage genome ????? is a more defined system. Recent research have found out that the Rho termination