What aspect of protein expression is controlled in both prokaryotes and eukaryotes?

The aspect of protein expression that is controlled in both prokaryotes and eukaryotes is the regulation of protein expression. Both types of organisms utilize complex mechanisms to control when and how much protein is produced from genes. In prokaryotes, this often involves transcription factors that bind to specific DNA sequences to enhance or inhibit transcription, while in eukaryotes, regulation occurs at multiple levels including transcription, RNA processing, translation, and post-translational modifications.

Protein expression encompasses the entire process from gene transcription to mRNA translation into proteins, making the regulation of protein expression a pivotal control point in cellular function. Since the core concept of regulating the quantity and timing of protein production is fundamental to both prokaryotic and eukaryotic cells, understanding this regulation is crucial to studying cellular biology in both domains.