Molecular mechanisms of nuclear pore complex biogenesis

The NPC is a massive ~100 MD complex that is built from hundreds of proteins. It spans the two membranes of the nuclear envelope and controls all molecular traffic between the nucleus and cytoplasm. Understanding the mechanisms behind the assembly of this structure is a significant challenge and represents a fundamental question in cell biology. Our work has identified key players in the early steps of assembly, but we are in need of a better understanding of the biochemical and structural intermediates and the order by which they are assembled to fully elucidate the assembly process. Moreover, a mechanistic understanding of how the inner and outer nuclear membranes are fused represents a key challenge that we actively investigate by exploring mechanisms of membrane bending and fusion.

Quality control of NPC assembly

The NPC imposes a barrier to movement of macromolecules across the nuclear envelope – this compartmentalization is essential for normal cell function. Indeed, disruption of nuclear compartmentalization is associated with various diseases including cancers and “laminopathies”. Moroever, recent work supports that the loss of the function of the NPC-diffusion barrier might contribute to the appearance of protein aggregates in the nucleus of old neurons – a hallmark of neurodegeneration. We have identified a surveillance mechanism that ensures proper NPC assembly by clearing and degrading defective NPC assembly intermediates. Morevoer, in a asymmetric division model like budding yeast, we have also explored mechanisms that both retain defective NPCs in mothers and promote the passage of functional NPCs to daughters thus ensuring daughter lifespan.

Mechanism of nuclear transport through the NPC

Despite several decades of research, we still do not have a complete mechanistic understanding of how macromolecules traffic through the NPC. There is a consensus that nucleoporins containing repeats of Phe-Gly (FG) are essential for the transport mechanism, but how the different “flavors” of FG-nups come together within a cylindrical architecture remains ill-defined.

Genome organization at the nuclear periphery

In the vast majority of cell types there is a clear organization to the genome such that heterochromatin associates with the nuclear envelope. Thus, the nuclear envelope has long been considered an architectural element that helps to define the 3D-organization of the genome, while also directly contributing to gene silencing and activation. Our lab focuses on integral inner nuclear membrane proteins that we helped identify as models to illuminate function at the nuclear periphery.

Role of nucleoporins during differentiation and development

Several recent studies support that nup malfunction leads to defects in development. The central challenge is to understand whether this loss of nup function reflects a defect in the nuclear transport of specific developmental regulators, or, whether nups function outside of the NPC. We have started several collaborations in diverse developmental models to begin to answer this question.