The St. Marianna Medical Journal
Online ISSN : 2189-0285
Print ISSN : 0387-2289
ISSN-L : 0387-2289
original article
UBE3B and UBE3C Functionally Regulate Cell Proliferation Through the Ubiquitin-proteasome System
Tomoko TsurugaToshio KumaiMaiko Okada
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JOURNAL FREE ACCESS

2017 Volume 45 Issue 3 Pages 149-159

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Abstract

Proper regulation of intracellular protein levels is essential in maintaining cellular homeostasis. The ubiquitin-proteasome system plays a central role in this regulation by degrading ubiquitinated-substrates in a target-specific manner. The abnormal enhancement of proteasomal activity in cancer tissues is closely related to cancer cell proliferation or survival. Therefore, it is important that we elucidate the underlying mechanism as a basis for cancer treatments with proteasome inhibitors. Here, we focused on the proteasomal regulator UBE3C and UBE3B, another highly homologous protein. Although these factors have been hypothesized to contribute to cell proliferation through proteasome regulation, their exact roles are largely unclear. In this report, we showed that UBE3B is required for cell proliferation. Although the cellular function of UBE3B is not known thus far, it is now clear that UBE3B co-localizes with the proteasome component in the nucleus and represses the aggregation or accumulation of ubiquitinated substrates. These results suggest that proper proteasomal regulation by UBE3B contributes to cell proliferation. In addition, UBE3B co-localizes with UBE3C, and the decreased proliferation of depleted UBE3B was slightly canceled by the depletion of both proteins. Taken together, UBE3C may modulate the function of UBE3B in cell proliferation.
Going forward, it is imperative that we clarify the relationship between the expression pattern of these factors and proteasomal function. This will help to ascertain the role of these factors as potential proteasome inhibitors in cancer therapy.

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© 2017 St. Marianna University Society of Medical Science
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