Stalling

 Almost all the biological processes in living systems are highly regulated to ensure that there is no error, or that the error rate is significantly low. 

Errors are not tolerated in nature. A small mistake can threaten the survival of the cell. So nature has evolved these mechanisms, fact-checking and proofreading of mistakes. 

Starting from DNA polymerase. It is one of the most accurate enzymes considering the rate at which it polymerises the DNA. Errors happen very rarely which are then corrected by some proofreading mechanism. 

Errors happen while RNA polymerases transcribe the template DNA into RNA. Unlike RNA errors in DNA is less tolerated. Errors in RNA are allowed to some extent because they could be the seed for evolution and also RNA is temporary. It is going to be degraded once its function is complete.

In rare instances, when mistakes do happen, when there are misincorporation of bases the RNA polymerase pauses and then backtracks. Once backtracked these complexes can remain in that state for long periods of time, which is not good for the stability of the genome. The RNA polymerase has to escape and resume transcription. 

RNA polymerase can by itself cleave off the misincorporated bases but it is very slow under physiological conditions. 

There are certain proteins that bind to the secondary channel of the RNA polymerase that enhances its cleavage activity upon binding. They are called the Gre factors. There are several other proteins that bind to the same channel and bring about a different function. 

And just as in transcription, stalling occurs during translation as well. The stalled ribosomes in the endoplasmic reticulum are marked by a protein called UFM1. It is still not a well-understood topic and there are ongoing research on the same.