Figure 1. Ideogram of ubiquitination signalling pathway in oral squamous cell carcinoma (OSCC). (a) A tissue microarray spot of an OSCC case (haematoxylin & eosin staining, original magnification 40×, 100×) (b) The Ubiquitin-Proteasome System (Ub-PS) recognizes and targets a broad spectrum of protein substrates. The ubiquitin-depended intracellular cascade includes a series of interactions between molecules such as E1/E2/E3 enzymes/ligases targeting ribosome protein domains (40S/60S subunits). The ubiquitination-deubiquitination procedure secures protein potential in a perfect balance promoting normal cell metabolism.