Suchergebnisse

The epidemics of AIDS, SARS, avian flu, MERS-CoV and SARS-CoV2 are examples of viral infections which, starting from local outbreaks, spread in many different countries or even became pandemics. Reports of novel viruses emerging from remote areas of the world and able to infect the human population, are not anymore confined to medical bulletins, but are being found everyday in newspapers and public media. This, because it is now well understood that every outbreak, small and remote it may be, can rapidly evolve into a worldwide health emergency. Dealing with such situations requires high forecasting ability starting from the available data and deep knowledge of the many factors influencing the spread of a viral outbreak. In turn, such ability stems from the study of the life cycle and pathogenetic mechanisms of the viruses. Understanding the biology of viruses and the relationships between emerging viral pathogens and the anthropic influences on the environment is the key to develop new drugs and vaccines, but also to genetically manipulate viruses for gene therapy applications.

p15PAF is an oncogenic intrinsically disordered protein that regulates DNA replication and lesion bypass by interacting with the human sliding clamp PCNA. In the absence of DNA, p15PAF traverses the PCNA ring via an extended PIP-box that contacts the sliding surface. Here, we probed the atomic-scale structure of p15PAF-PCNA-DNA ternary complexes. Crystallography and MD simulations show that, when p15PAF occupies two subunits of the PCNA homotrimer, DNA within the ring channel binds the unoccupied subunit. The structure of PCNA-bound p15PAF in the absence and presence of DNA is invariant, and solution NMR confirms that DNA does not displace p15PAF from the ring wall. Thus, p15PAF reduces the available sliding surfaces of PCNA, and may function as a belt that fastens the DNA to the clamp during synthesis by the replicative polymerase (pol δ). This constraint, however, may need to be released for efficient DNA lesion bypass by the translesion synthesis polymerase (pol η). Accordingly, our biochemical data show that p15PAF impairs primer synthesis by pol η-PCNA holoenzyme against both damaged and normal DNA templates. In light of our findings, we discuss the possible mechanistic roles of p15PAF in DNA replication and suppression of DNA lesion bypass. ; Italian Association for Cancer Research [iCARE fellowship from AIRC and the European Commission to A.D.B. and AIRC Grant IG14718 to S.O., IG20762 to G.M and MFAG18811 to E.C.]; Spanish Ministry of Economy and Competitiveness [CTQ2017-83810-R grant to F.J.B.]; CIC bioGUNE acknowledges MINECO for the Severo Ochoa Excellence Accreditation [SEV-2016-0644]; S.B-V. and A.G.-M. acknowledge fellowships from MINECO [BES-2013-063991 and BES-2015-075847]; M.R.-M. is supported by a pre-doctoral fellowship from the Basque Government [PRE_2016_2_0249]. Funding for open access charge: University of Leicester. ; Peer reviewed