Final answer:
Post-translational modifications affect gene expression primarily through phosphorylation and the addition of functional groups, altering protein activity and location, thereby influencing gene regulation mechanisms.
Step-by-step explanation:
Post-translational modifications (PTMs) affect gene expression through a variety of mechanisms. Two pivotal ways include phosphorylation of proteins and the addition of functional groups such as methyl, phosphate, or acetyl groups. Phosphorylation can alter the activity of a protein by changing its ability to bind to DNA or other proteins, impacting factors such as chromosomal accessibility, transcription, mRNA stability, and translation. This modification allows a cell to promptly adjust protein levels in response to external stimuli, like stress or nutrient availability. Similarly, PTMs can determine the protein's location - whether in the nucleus, cytoplasm, or plasma membrane, which can influence gene expression by affecting which processes the protein can regulate or be involved in.