%0 Generic
%A Özgür, Sevim
%D 2011
%F heidok:12956
%K Pat1b , mRNA abbau , Decapping , P-bodyPat1b , mRNA decay , decapping , deadenylation , P-body
%R 10.11588/heidok.00012956
%T Characterization of human Pat1b, an essential P-body protein that links deadenylation to decapping in 5’ to 3’ mRNA decay
%U https://archiv.ub.uni-heidelberg.de/volltextserver/12956/
%X In eukaryotic cells, degradation of many mRNAs is initiated by removal of the polyA tail followed by decapping and 5’ to 3’ exonucleolytic decay. Although the order of these events is well established, we are still lacking a mechanistic understanding of how deadenylation and decapping are linked. During my PhD studies, I characterized the human Pat1b protein and showed that Pat1b links the deadenylation complex to the decapping complex both physically and functionally. Pat1b is tightly associated with the Ccr4-NOT deadenylation complex as well as with the Dcp1-Dcp2 decapping complex. In addition, Pat1b overexpression increases the association of the deadenylation complex with the decapping complex. When tethered to a reporter mRNA, Pat1b induces its rapid degradation. Pat1b-mediated mRNA decay depends on the deadenylase Caf1a and the decapping enzyme Dcp2, indicating that these interactions are functionally important. Moreover, Pat1b interacts with the decapping enhancers Rck, the Lsm1-7 complex, Hedls and Edc3. Pat1b interacts with the deadenylation complex, the decapping complex and the decapping enhancers via at least three different domains, suggesting that Pat1b serves as a scaffolding protein. Together, the data provide evidence that human Pat1b is a central component of the mRNA decay machinery that connects deadenylation with decapping. Most enzymes of the 5’ to 3’ mRNA decay pathway, including the Ccr4-NOT deadenylation complex, are localized in cytoplasmic foci called processing (P) bodies. I could show that Pat1b is required for P-body formation, and that it strongly induces P-body numbers when overexpressed. My data indicate that an amino-terminal region within Pat1b serves as an aggregation-prone domain that nucleates P-bodies, whereas an acidic domain controls the size of P-bodies. Although Rck specifically interacts with the acidic domain of Pat1b, point mutations in Pat1b that abolish the Rck interaction did not alter P-body size. On the other hand, I also identified point mutations in Rck that abolish Pat1b binding, and found that Rck needs to associate with PAt1b in order to promote P-body formation. Furthermore, I purified Pat1b and identified additional binding partners via mass spectrometry. Further characterization of these interactions may help to understand how Pat1b controls P-body numbers and size, and what additional functions Pat1b may have.