Structural Analysis of the Pin1-CPEB1 interaction and its potential role in CPEB1 degradation

Abstract

The Cytoplasmic Polyadenylation Element Binding proteins are RNA binding proteins involved in the translational regulation of mRNA. During cell cycle progression, CPEB1 is labeled for degradation by phosphorylation-dependent ubiquitination by the SCFβ−TrCP ligase. The peptidyl-prolyl isomerase Pin1 plays a key role in CPEB1 degradation. Conditioned by the cell cycle stage, CPEB1 and Pin1 interactions occur in a phosphorylation-independent or -dependent manner. CPEB1 contains six potential phosphorylatable Pin1 binding sites. Using a set of biophysical techniques, we discovered that the pS210 site is unique, since it displays binding activity not only to the WW domain but also to the prolyl-isomerase domain of Pin1. The NMR structure of the Pin1 WW-CPEB1 pS210 (PDB ID: 2n1o) reveals that the pSerPro motif is bound in trans configuration through contacts with amino acids located in the first turn of the WW domain and the conserved tryptophan in the β3-strand. NMR relaxation analyses of Pin1 suggest that inter-domain flexibility is conferred by the modulation of the interaction with peptides containing the pS210 site, which is essential for degradation.

Activity-dependent isomerization of Kv4.2 by Pin1 regulates cognitive flexibility

“…These models were primarily based on PDB: 2N10 (ref. 73 ) for the WW domain, and PDB: 2Q5A 74 for the Catalytic domain. Modeling was done by an interplay of "manual" manipulation with UCSF Chimera 75 and energy minimization (to prevent steric overlap and optimize salt-bridges and hydrogen bonds) with CHARMM 76 .…”

Structure and function of the human parvulins Pin1 and Par14/17

“…The affinity of such target motifs is a few times higher to the WW domain than to the PPIase domain (Lu et al, 1999b). Hence, on the one hand the WW-domain is able to target the same motifs as the catalytic domain does (Schelhorn et al, 2015), but on the other hand, the WW domain can select and bind a special motif, thereby guiding hPin1 to a nearby second targeting side amenable for its catalytic domain . The latter mechanism is supposed for multiphosphorylated target proteins such as the RNA-PolII (Kops et al, 2002) or Tau (Smet et al, 2005).…”

“…It transports the PPIase to the cellular nucleus, dominates localization in nuclear speckles (Rippmann et al, 2000) and, thus, limits the putative substrates to a certain number of nuclear proteins (Lu et al, 1999b). The WW-domain is specific against a set of binding motifs similar to those known to be isomerized by the catalytic domain (Lu et al, 1999b;Schelhorn et al, 2015), although certain differences have been implied recently (Innes et al, 2013). The affinity of such target motifs is a few times higher to the WW domain than to the PPIase domain (Lu et al, 1999b).…”

“…, located in the β 1 -strand, mainly facilitates the coordination of the phosphate group (Schelhorn et al, 2015) (Figure 3, right). Recent studies reported a binding preference towards Xaa-Pro-Pro motifs (Innes et al, 2013).…”

Changes in the folding landscape of the WW domain provide a molecular mechanism for an inherited genetic syndrome

“…The fold of WW domains is in general well known, consisting of a stable, triple stranded beta sheet 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 . The solution NMR structures of several WW domains have been determined revealing a common fold but also different degrees of conformational stability.…”