Errors in replication and damage to DNA have two consequences;
One is, of course, the introduction of permanent changes to the DNA (mutations), which can alter the coding sequence of a gene or its regulatory sequences.
The second consequence is that some chemical alterations to the DNA prevent its use as a template for replication and transcription

TLS Online TPP Program

#Id: 789

#Unit 3. Fundamental Processes

Rho factor is an essential protein in E. coli that causes transcription termination, accounts for almost half of E. coli terminators.

TLS Online TPP Program

#Id: 790

#Unit 3. Fundamental Processes

Sequences of Rho dependent transcription termination

1. Rho binds a rut site. 

2. The rho factor then tracks along the RNA until it catches up to RNA polymerase. 

3. When the RNA polymerase reaches the termination site, rho first freezes the structure of the polymerase and then invades the exit channel to destabilize the enzyme, causing it to release the RNA. 

4. Pausing by the polymerase at the site of termination allows time for rho factor to translocate to the hybrid stretch.

TLS Online TPP Program

#Id: 791

#Unit 3. Fundamental Processes

A rut site has a sequence rich in C -41% and poor in G preceding the actual site(s) of termination. The sequence corresponds to the 3’ end of the RNA.

 

TLS Online TPP Program

#Id: 792

#Unit 3. Fundamental Processes

C is by far the most common base (41%) and G is the least common base (14%) in rut sites, vary in length.  As a general rule, the efficiency of a rut site increases with the length of the C-rich/G-poor region.

TLS Online TPP Program

#Id: 793

#Unit 3. Fundamental Processes

Rho is a member of the family of hexameric ATP-dependent helicases. Each subunit has an RNA-binding domain and an ATP hydrolysis domain.

TLS Online TPP Program

#Id: 794

#Unit 3. Fundamental Processes

Rho activity is impeded when ribosomes are translating an mRNA.