nup154 genetically interacts with cup and plays a cell-type-specific function during Drosophila melanogaster egg-chamber development

Nucleoporin Nup154 is a Drosophila component of the nuclear pore complex (NPC), evolutionarily conserved from yeast to humans. While functional studies carried out in both yeast and metazoan cells indicated that Nup154 homologs are key elements of the NPC framework, the striking phenotypic specificity displayed by nup154 hypomorphic mutant alleles suggested that Nup154 might play additional roles in the context of the NPC. Actually, genetic analyses demonstrated that mutant nurse-cell nuclei do not undergo a normal chromosome dispersal process, uncovering an essential requirement for nup154 gene function during oogenesis. In this report, we show that Nup154 interacts genetically and physically with Cup, a germline-specific protein implicated in multiple aspects of female gametogenesis, including the regulation of the nurse-cell chromosome structure. The two proteins colocalize in vivo and are co-immunoprecipitated from ovarian extracts. Moreover, cup, nup154 double mutants exhibit much stronger oogenesis defects than single mutants. Our findings delineate an intriguing scenario where an ubiquitous nucleoporin might directly influence specialized developmental events.