Acetylation, through the post-transcriptional modification of histones, is a well-established regulator of gene transcription. More recent research has also identified an important role for acetylation in the regulation of non-histone proteins, both inside and outside the nucleus. As a fast (and reversible) post-translational process, acetylation allows cells to rapidly alter the function of existing proteins, making it ideally suited to biological programmes that require an immediate response to changing conditions. Using metabolic programmes as an example, the present chapter looks at how reversible acetylation can be used to regulate important enzymes in an ever-changing cellular environment.
Mitochondria are highly dynamic cellular organelles, with the ability to change size, shape and position over the course of a few seconds. Many of these changes are related to the ability of mitochondria to undergo the highly co-ordinated processes of fission (division of a single organelle into two or more independent structures) or fusion (the opposing reaction). These actions occur simultaneously and continuously in many cell types, and the balance between them regulates the overall morphology of mitochondria within any given cell. Fission and fusion are active processes which require many specialized proteins, including mechanical enzymes that physically alter mitochondrial membranes, and adaptor proteins that regulate the interaction of these mechanical proteins with organelles. Although not fully understood, alterations in mitochondrial morphology appear to be involved in several activities that are crucial to the health of cells. In the present chapter we discuss the mechanisms behind mitochondrial fission and fusion, and discuss the implications of changes in organelle morphology during the life of a cell.