van den Heuvel S (2004) Curr Biol "Protein degradation: CUL-3 and BTB--partners in proteolysis."

van den Heuvel S

[Curr Biol, 2004]

In early C. elegrans embryos, the transition from meiosis to mitosis requires degradation of the MEI-1 protein. A novel class of SCF-like ubiquitin ligases has been identified that mediates this process. These ligases contain the CUL-3 scaffold at their core and use a BTB-domain protein in substrate recognition.

Quarmby L (2000) J Cell Sci "Cellular Samurai: katanin and the severing of microtubules."

Quarmby L

[J Cell Sci, 2000]

Recent biochemical studies of the AAA ATPase, katanin, provide a foundation for understanding how microtubules might be severed along their length. These in vitro studies are complemented by a series of recent reports of direct in vivo observation of microtubule breakage, which indicate that the in vitro phenomenon of catalysed microtubule severing is likely to be physiological. There is also new evidence that microtubule severing by katanin is important for the production of non-centrosomal microtubules in cells such as neurons and epithelial cells. Although it has been difficult to establish the role of katanin in mitosis, new genetic evidence indicates that a katanin-like protein, MEI-1, plays an essential role in meiosis in C. elegans. Finally, new proteins involved in the severing of axonemal microtubules have been discovered in the deflagellation system of Chlamydomonas.

Wulczyn FG et al. (2010) Adv Exp Med Biol "MiRNA need a TRIM regulation of miRNA activity by Trim-NHL proteins."

Franzoni E, Cuevas E, Rybak A, Wulczyn FG

[Adv Exp Med Biol, 2010]

Trim-NHL proteins are defined by RING, B-Box and Coiled-coil protein motifs (referred to collectively as the Trim domain) coupled to an NHL domain. The C. elegans, D. melanogaster, mouse and human Trim-NHL proteins are potential and in several cases confirmed, E3 ubiquitin ligases. Current research is focused on identifying targets and pathways for Trim-NHL-mediated ubiquitination and in assessing the contribution of the NHL protein-protein interactiondomain for function and specificity. Several Trim-NHL proteins were discovered in screens for developmental genes in model organisms; mutations in one of the family members, Trim32, cause developmental disturbances in humans. In most instances, mutations that alter protein function map to the NHL domain. The NHL domain is a scaffold for the assembly of a translational repressor complex by the Brat proto-oncogene, a well-studied family member in Drosophila. The link to translational control is common to at least four Trim-NHLs that associate with miRNA pathway proteins. So far, two have been shown to repress (Mei-P26 and Lin41) and two to promote (NHL-2, Trim32) miRNA-mediated gene silencing. In this chapter we will describe structure-function relations for each of the proteins and then focus on the lessons being learned from these proteins about miRNA functions in development and in stem cell biology.