Through epidemiological and biochemical studies the role of mucosal HPV types in human cancer has been confirmed and the molecular mechanisms underlying the transformation process have been... Show moreThrough epidemiological and biochemical studies the role of mucosal HPV types in human cancer has been confirmed and the molecular mechanisms underlying the transformation process have been elucidated. However, although research on the cutaneous HPV types is progressing fast, many questions remain unanswered regarding their potential role in human skin carcinogenesis.This thesis describes the characterization of the biological properties of E6 and E7 proteins from mucosal and cutaneous HPV types using novel or previously described assays and models. First, we describe the development and use of an in vitro systems to evaluate and quantify the ability of the oncoprotein E7 to associate with pRb (chapter 2). However, we show that this binding although indicative of a high risk HPV type, does not necessarily correlate with in vivo carcinogenicity (chapter 3) and that other in vitro studies are essential to asses the carcinogenicity of any given HPV type. Next we focused on the cutaneous HPV type 38, which displays in vitro transforming properties and appears to be frequently present in NMSC. We show that this cutaneous HPV type can increase the risk for development of skin cancer (chapter 4)and we describe a novel HPV transformation mechanism (chapter 5). Show less
The p53 protein is an important tumor suppressor that acts as a key regulator of the integrity of the genome. Two essential regulators of the p53 protein are Mdm2 and its homologue Mdmx. Like Mdm2,... Show moreThe p53 protein is an important tumor suppressor that acts as a key regulator of the integrity of the genome. Two essential regulators of the p53 protein are Mdm2 and its homologue Mdmx. Like Mdm2, Mdmx represses p53-induced transcription. However, Mdmx cannot ubiquitinate or degrade p53 opposed to Mdm2. In chapter 2, studies aimed to better understand the functional differences between Mdmx and Mdm2. By generation of hybrid constructs between Mdmx and Mdm2, we found that in addition to a complete RING domain of Mdm2, also an internal acidic domain is required for p53 ubiquitination and degradation. In chapter 3 the role of Mdmx in human tumor formation is described. The results show that the mdmx gene can function as an oncogene and demonstrate that the transforming function of the Mdmx protein is dependent on its ability to interact with p53. In chapter 4, the regulation of Mdmx stability is described. We demonstrate that the stability of Mdmx is determined by a balance in de-ubiquitination by HAUSP and ubiquitination by Mdm2. Chapter 5 the results of initial studies on the role of SUMO conjugation in Mdmx function are shown. Show less
