Sunday 13 July 2003
Ubiquitination is a versatile tool of eukaryotic cells for controlling the stability, function and subcellular localization of proteins.
The variety of cellular processes regulated by ubiquitination demands high substrate specificity of the ubiquitination machinery as well as the existence of diverse downstream effector proteins interacting with ubiquitinated substrates.
Most of these cellular effectors are characterized by a modular composition of ubiquitin-binding motifs and further domains mediating specific functions.
Ubiquitin targets proteins for degradation by the proteasome.
Several other functions of ubiquitin are independent of proteasomal degradation. These functions include the novel signaling roles of ubiquitin in DNA repair and the activation of protein kinases such as IkappaB kinase.
A form of polyubiquitin chain linked through lysine-63 of ubiquitin plays an important regulatory role.
Monoubiquitination has signaling roles that are distinct from those of polyubiquitination, as illustrated from the studies of DNA repair.
ubiquitin-related protein motifs (UBA, UIM, UBD and UBX domains)
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