Altruism

Altruistic acts serve to benefit the individual’s close relatives, or kin. They enhance the fitness of other individuals—their offspring—at a cost to themselves.

TLS Online TPP Program

#Id: 6318

#Unit 3. Fundamental Processes

Rho binds to a sequence within the transcript upstream of the site of termination. This sequence is called a rut site (an acronym for rho utilization). 

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

TLS Online TPP Program

#Id: 6319

#Unit 3. Fundamental Processes

A rut site has a sequence rich in C 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: 6320

#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: 6321

#Unit 3. Fundamental Processes

After binding to the rut site, rho uses its helicase activity, driven by ATP hydrolysis, to translocate along RNA until it reaches the RNA polymerase

TLS Online TPP Program

#Id: 6322

#Unit 3. Fundamental Processes

Nonsense mutation in one gene of a transcription unit was found to prevent the expression of subsequent genes in the unit even though both genes had their own ribosome binding sites, an effect called polarity.

TLS Online TPP Program

#Id: 6323

#Unit 3. Fundamental Processes

Rho-dependent termination sites within a transcription unit are usually masked by translating ribosomes and therefore rho cannot act on downstream RNA polymerases