You just performed an aexperiment in which you investigated RNA synthesis in vit

Question

You just performed an aexperiment in which you investigated RNA synthesis in vitro . Interestingly, the RNA molecules synthesized in vitro by RNA polymerase acting alone are longer tna those made in vivo. You hypothesized that something was missing from the in vitro system that is present in the in vivo. To check, you added extra cell extract and found that the correct termination took place. You concluded that a specific protein in the cell was responsible for these results. Then, you performed an experiment where the protein was added to the RNA synthesis reaction at different times after initiaiton of RNA synthesis. Explain how inserting this new protein increases the length of the RNA molecule. Is this a new protein identified?

Explanation / Answer

I assume the cells are prokaryotic.

The RNA molecules made in vitro are larger and those made in vivo are comparitively shorter. I postulate that the protein being added is a termination factor (in case of bacteria, termination factor is 'rho'). This factor helps in termination of the process of transcription at correct time by binding to the RNA polymerase and not allowing further transcription.

Now an experiment is done wherein, rho- protein is added to the in vitro cultures at different times during the transcription. This may lead to different sizes of RNA transcripts being formed. It is because, when rho protein is added, transcription will be terminated. This will occur earlier in the cells which are yet to reach the end of transcription and hence will produce premature transcripts. This will result in different lengths of transcripts being produced.

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