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Title: Regulation of APOBEC3 activity and HIV-1 replication by P-body associated proteins
Author: Phalora, Prabhjeet
Awarding Body: King's College London (University of London)
Current Institution: King's College London (University of London)
Date of Award: 2012
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The APOPEC3 family of cytidine deaminases play an important role in host mediated antiviral defence against retroelements, including HIV-1. Although much has been discerned regarding the anti-viral nature of these proteins, their cellular function, as well as mechanisms of functional regulation and cellular co-factors, remains poorly defined. To address this, several cellular proteins that interact with APOBEC3G (A3G) have now been identified. The most intriguing of these are the Argonaute proteins, as the interaction is at least partially resistant to RNase treatment. The Argonautes are integral components of RISC, which is involved in miRNA mediated translational repression and mRNA decay. Components of this pathway, as well as A3G and silenced mRNAs have been shown to localise to discrete cytoplasmic foci termed mRNA Processing (P) Bodies. These foci have very recently been implicated in influencing viral life cycles. However, the functional relevance of the interaction with the Argonaute proteins and localisation to P-bodies, to APOBEC3 anti-viral and cellular activity is currently unknown and therefore was investigated in more detail. It has been found that the ability of the APOBEC3 proteins to interact with Argonaute 2 does not closely correlate with their anti-viral phenotypes. Further, knockdown of Argonaute 2 did not impact upon APOBEC3 mediated viral inhibition, suggesting that this cellular protein is not required for this process. Conversely, the role of APOBEC3 proteins in the regulation of cellular RNA was also examined. However, the APOBEC3 proteins did not specifically affect the post-transcriptional regulatory pathways of miRNA mediated repression, siRNA mediated silencing or ARE mediated decay. Localisation of APOBEC3 proteins to mRNA Processing bodies, on the other hand, does correlate with their anti-viral activities, implying that subcellular localisation may be important for viral inhibition. However, depletion of P-bodies through knockdown of DDX6 and Lsm1, did not affect APOBEC3 restriction of HIV-1 or replication of HIV-1 in general. In sum, P-body associated proteins do not appear to regulate APOBEC3 anti-viral activity and thus may be more relevant to an as yet unidentified cellular function of this protein family.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available