The enzymes of the ubiquitylation pathway play a pivotal role in a number of cellular processes including the regulated and targeted proteasomal degradation of substrate proteins. Three classes of enzymes are involved in the process of ubiquitylation; activating enzymes (E1s), conjugating enzymes (E2s) and protein ligases (E3s). UBE2Q2 is a member of the E2 conjugating enzyme family. The cloning of human UBE2Q2 was first described by Crawford and Piwnica-Worms. (2001). UBE2Q2 has been found to be up-regulated in 85% of head and neck squamous cell carcinoma tumours, with an increase of 2.4-fold compared to normal tissue. Immunohistochemistry and in situ hybridization analysis on tumour tissue sections has revealed strong signals in the tumour cell islets, invasive epithelia, and dysplastic regions (Seghatoleslam et al., 2006). UBE2Q2 has been identified as a novel oncosuppressor that inhibits tumour growth and it is thought it could function as a novel diagnostic tool and potential therapeutic target for head and neck squamous cell carcinoma (Maeda et al., 2009). UBE2Q2 may play a role in cytoskeleton structure and regulation, as actin and 6 actin binding proteins have been shown to interact with UBE2Q2 (Seghatoleslam et al., 2006). Inhibition of UBE2Q2 following treatment of HeLa cells with Microtubule Inhibiting Agent (MIA) causes mitotic arrest and increased cytotoxicity, effects only observed in the absence of MIA suggesting UBE2Q2 is only involved in this response rather than having a more general role in mitosis (Banerjee et al., 2007).
Banerjee S, Brooks WS, Crawford DF (2007) Inactivation of the ubiquitin conjugating enzyme UBE2Q2 causes a prophase arrest and enhanced apoptosis in response to microtubule inhibiting agents. Oncogene 26, 6509-17.
Crawford DF, Piwnica-Worms H (2001) The G(2) DNA damage checkpoint delays expression of genes encoding mitotic regulators. J Biol Chem 276, 37166-77.
Maeda H, Miyajima N, Kano S, Tsukiyama T, Okumura F, Fukuda S, Hatakeyama S (2009) Ubiquitin-conjugating enzyme UBE2Q2 suppresses cell proliferation and is down-regulated in recurrent head and neck cancer. Mol Cancer Res 7, 1553-62.
Seghatoleslam A, Zambrano A, Millon R, Ganguli G, Argentini M, Cromer A, Abecassis J, Wasylyk B (2006) Analysis of a novel human gene, LOC92912, overexpressed in hypopharyngeal tumours. Biochem Biophys Res Commun 339, 422-9.