There are a number of ways via which protein expression patterns can be moderated:
1. Transcriptional control
- Protein expression can be regulated by controlling to amount of transcription (less mRNA = less protein)
- This level of control is achieved primarily through the coordinated effects of transcription factors and regulatory proteins
2. RNA processing control
- This involves regulating the formation of mature mRNA in eukaryotes (e.g. 5’-capping and 3’-polyadenylation)
- These processes are necessary to help direct the mRNA to the ribosome and prevent its premature degradation
3. RNA transport control
- In eukaryotes, RNA must be transported out of the nucleus (through nuclear pores) in order to associate with the ribosome
- If this transport is prevented, the related protein cannot by synthesised
4. Translational control
- Protein expression can also be regulated by controlling the amount of translation
- This may involve inhibiting ribosomal subunit assembly or actively targeting mRNA for degradation
5. Protein activity control
- Protein expression patterns may also be affected by the rate of protein degradation
- Post-translational modifications (such as ubiquitination or phosphorylation) may target proteins for destruction
Mechanisms of Regulating Protein Expression Levels
