Molecular mechanisms underlying the functional multiplicity of human DKC1 gene

Hypomorphic mutations of the DKC1 gene cause the Xlinked dyskeratosis congenita, an inherited multisystemic disorder characterized by a variety of symptoms, including mucocutaneous features, stem cell dysfunction, bone marrow failure, and increased susceptibility to cancer. DKC1 encodes an evolutionarily conserved protein, called dyskerin, whose activity is essential for cellular vitality. Dyskerin participates in at least two functional ribonucleoprotein (RNP) complexes that play essential roles in the cell. The protein is in fact an essential component of H/ACA snoRNPs, which are involved in the processing and pseudouridylation of rRNAs. In addition, through its binding to the telomerase RNA component (TERC), that contains an H/ACA RNA motif, dyskerin participates in the active complex of telomerase, ensuring telomeres stability and maintenance. In order to investigate and characterize in more detail the effects triggered by DKC1 loss of function on human cells, we generated a stable cellular model able to reduce gene expression, upon inducible RNA interference, without affecting the expression of the alternatively spliced cytoplasmic isofom 3. I focussed my analyses on the effects triggered by dyskerin depletion well before telomere erosion, in order to define the spectrum of telomere independent outcomes. Intriguingly, I found that dyskerin depletion affected cell adhesion. In fact, dyskerin dowregulation perturbed both cell-cell and cell substrate adhesion, causing reduced expression of some proteins involved in the tight and adherens junctions, and in the focal adhesions. Moreover, coimmunoprecipitations analyses revealed interactions between dyskerin and some component of focal adhesions, while confocal microscopy indicates that this interaction can occur at level of the plasma membrane. Finally, I observed that dyskerin depletion alter cell morphology and increases cell motility. Altogether, these results could be of valuable help to understanding the puzzling relationship that links pseudouridine synthases loss-of-function to cancer predisposition.