Mechanism of USP7/HAUSP activation by its C-terminal ubiquitin-like domain and allosteric regulation by GMP-synthetase.

The ubiquitin-specific protease USP7/HAUSP regulates p53 and MDM2 levels, and cellular localization of FOXO4 and PTEN, and hence is critically important for their role in cellular processes. Here we show how the 64 kDa C-terminal region of USP7 can positively regulate deubiquitinating activity. We present the crystal structure of this USP7/HAUSP ubiquitin-like domain (HUBL) comprised of five ubiquitin-like (Ubl) domains organized in 2-1-2 Ubl units.

The deubiquitinating enzyme USP26 is a regulator of androgen receptor signaling.

The androgen receptor (AR) is a member of the nuclear receptor superfamily and is essential for male sexual development and maturation, as well as prostate cancer development. Regulation of AR signaling activity depends on several posttranslational modifications, one of these being ubiquitination. We screened a short hairpin library targeting members of the deubiquitination enzyme family and identified the X-linked deubiquitination enzyme USP26 as a novel regulator of AR signaling.

A genomic and functional inventory of deubiquitinating enzymes.

Posttranslational modification of proteins by the small molecule ubiquitin is a key regulatory event, and the enzymes catalyzing these modifications have been the focus of many studies. Deubiquitinating enzymes, which mediate the removal and processing of ubiquitin, may be functionally as important but are less well understood. Here, we present an inventory of the deubiquitinating enzymes encoded in the human genome.

Functional annotation of deubiquitinating enzymes using RNA interference.

Protein ubiquitination is a dynamic process, depending on a tightly regulated balance between the activity of ubiquitin ligases and their antagonists, the ubiquitin-specific proteases or deubiquitinating enzymes. The family of ubiquitin ligases has been studied intensively and it is well established that their deregulation contributes to diverse disease processes, including cancer. Much less is known about the function and regulation of the large group of deubiquitinating enzymes.

The deubiquitinating enzyme USP1 regulates the Fanconi anemia pathway.

Protein ubiquitination and deubiquitination are dynamic processes implicated in the regulation of numerous cellular pathways. Monoubiquitination of the Fanconi anemia (FA) protein FANCD2 appears to be critical in the repair of DNA damage because many of the proteins that are mutated in FA are required for FANCD2 ubiquitination. By screening a gene family RNAi library, we identify the deubiquitinating enzyme USP1 as a novel component of the Fanconi anemia pathway.

Loss of the cylindromatosis tumour suppressor inhibits apoptosis by activating NF-kappaB.

Protein modification by the conjugation of ubiquitin moieties--ubiquitination--plays a major part in many biological processes, including cell cycle and apoptosis. The enzymes that mediate ubiquitin-conjugation have been well-studied, but much less is known about the ubiquitin-specific proteases that mediate de-ubiquitination of cellular substrates. To study this gene family, we designed a collection of RNA interference vectors to suppress 50 human de-ubiquitinating enzymes, and used these vectors to identify de-ubiquitinating enzymes in cancer-relevant pathways.

Reversal of senescence in mouse fibroblasts through lentiviral suppression of p53.

Senescence is generally defined as an irreversible state of G(1) cell cycle arrest in which cells are refractory to growth factor stimulation. In mouse embryo fibroblasts (MEFs), induction of senescence requires the presence of p19(ARF) and p53, as genetic ablation of either of these genes allows escape from senescence and leads to immortalization. We have developed a lentiviral vector that directs the synthesis of a p53-specific short hairpin transcript, which mediates stable suppression of p53 expression through RNA interference.

Requirements for RNA heterodimerization of the human immunodeficiency virus type 1 (HIV-1) and HIV-2 genomes.

Retroviruses are prone to recombination because they package two copies of the RNA genome. Whereas recombination is a frequent event within the human immunodeficiency virus type 1 (HIV-1) and HIV-2 groups, no HIV-1/HIV-2 recombinants have been reported thus far. The possibility of forming HIV-1/HIV-2 RNA heterodimers was studied in vitro.

Regulated HIV-2 RNA dimerization by means of alternative RNA conformations.

The dimer initiation site (DIS) hairpin of the HIV-2 untranslated leader RNA mediates in vitro dimerization through 'loop-loop kissing' of a loop-exposed palindrome sequence. Premature RNA dimerization must be prevented during the retroviral life cycle. A regulatory mechanism has been proposed for the HIV-1 leader RNA that can adopt an alternative conformation in which the DIS motif is effectively masked by long-distance base pairing with upstream leader sequences.