Vol 1, No 2 (2014)

Ubiquitination of signaling receptors triggers their endocytosis to restrict the extent of cell signaling. Type 1 interferon (IFN1) eliminates its receptor from cell surface via stimulating the ubiquitination of its IFNAR1 chain. While it was suggested that this ubiquitination aids IFNAR1 internalization via relieving a steric hindrance of a linear motif within IFNAR1 from the endocytic machinery, the mechanisms involved remain poorly understood. Here we describe a specific role for two disparate ubiquitin acceptor sites within this receptor. These sites, Lys501 and Lys525 / 526, exhibit a preference for polyubiquitination via either Lys63- or Lys48‑linked chains (K63‑Ub and K48‑Ub, respectively). Whereas the SCFβTrcp E3 ubiquitin ligase controls either type of ubiquitination-dependent IFNAR1 endocytosis, the specificity of these processes is determined by two different E2 ubiquitin conjugating enzymes, Ubc13 and Cdc34. These enzymes can be directly used by SCFβTrcp E3 ubiquitin ligase to generate either K63‑Ub or K48‑Ub in vitro. Ubc13 is involved in IFNAR1 endocytosis driven by the K63‑Ub modification of Lys501, whereas the K48‑Ub-specific Cdc34 affects receptor endocytosis via ubiquitin conjugation that occurs on
Lys525 / 526. Both types of linkages combine to maximize IFNAR1 endocytosis otherwise suppressed by unfavorable conformation dependent on the presence of a conserved Pro470 within the intracellular domain of IFNAR1. We propose a model where alternate utilization of both E2s to assemble diverse polyubiquitin linkages cooperates to achieve IFNAR1 intracellular domain conformations and spatial arrangements that favor a maximal rate of receptor endocytosis.

5–10 % of breast cancer cases are hereditary, 30 % of them are caused by BRCA1 and BRCA2 mutations (breast / ovarian cancer syndrome). Average cumulative risks of breast and ovarian cancer in BRCA1 mutation carriers run up to 87 % and 44 %, correspondingly. The risk for contralateral breast cancer is also high: after 25 years, 62.9 % of patients with BRCA1 mutation who were younger than 40 years of age at first breast cancer develop contralateral breast cancer. The role of single nucleotide polymorphisms in BRCA1 and BRCA2 genes modifying breast and gynaecological cancer risks is actively studied. Genetic testing is performed as a part of genetic counselling. The main inclusion criteria are multiple affected family members with breast / ovarian cancer, breast cancer at young age (under 35–50 years), ovarian cancer at any age, male breast cancer, morphological features of breast cancer (triple-negative, medullar tumors), ethnicity (Jewish ancestry). High-risk individuals carrying BRCA mutations undergo specific surveillance, chemoprophylaxis and surgery protocols. Prophylactic bilateral mastectomy reduces breast cancer risk by 90–94 %.

Kidney cancer (renal cell carcinoma) is one of the major problems of modern urological oncology. In Russia renal cell carcinoma accounts
for 4.3 % of all cancers. The global incidence of renal cell carcinoma has increased over the past two decades. Worldwide renal cell carcinoma accounts for 3.6 % of all cancers and is 10th frequent malignancy. For some malignancies, for instance tumours of prostate, there are markers known that allowed improved early diagnostics. Kidney cancer, however, remains to be hard to diagnose and to treat, since the symptoms can be detected on advanced stages of the disease. In Russia 75.4 % of renal cell carcinoma cases detected at the stage of local and locally advanced disease. Though there are various target drugs on the market aimed to treat this disease, the results of renal cell carcinoma treatment did not reach any substantial success. Most of existing target drugs for kidney cancer treatment include inhibitors of a single signaling
pathway regulated by VHL1, which expression is lost in the vast majority of renal-cell carcinomas. Till now existing drugs did not reach sufficient efficacy. Therefore, it is highly important to search for new signaling pathways, regulating such cellular processes as proliferation, migration and apoptosis. Further, prognostic markers and therapy targets identified so far are not sufficient and poorly specific. Therefore identification and validation of new markers, and especially new specific targets for the treatment of kindey oncopathologies is highly important and timely task.