Proteostasis
Proper protein function relies on a balanced system of protein synthesis, folding, trafficking and degradation to ensure a homeostatic concentration of properly processed proteins in the organism. Disruptions in any one of these events can result in alterations in the level of proteins, the accumulation of misfolded proteins, and or the aggregation of proteins. Stress responses in the cytoplasm, mitochondria, and ER keep properly folded protein concentrations in check. These systems maintain proteostasis by up-regulating or down-regulating transcriptional and translational processing of proteins or by increasing protein degradation pathways. Many disease states in humans, such as cystic fibrosis, and Alzheimer's, Parkinson's and Huntington's diseases have been attributed to the breakdown of proteostasis systems in the cell.
DNA damage response
DNA damage can occur during normal recombination events or result from various insults, such as exposure to chemical mutagens or exposure to radiation. Metazoans have evolved mechanisms to detect, assess, and deal with any damage at specific checkpoints during the cell cycle. Studies in yeasts and mammals have identified several genes that are required for proper activation of cell cycle check-points following various types of DNA damage. However, in these metazoans, DNA damage can induce apoptosis as well. The inability to efficiently repair DNA damage or remove cells with severely damaged genomes has been linked to several human cancers.