A new subclass of nucleoporins that functionally interact with nuclear pore protein NSP1

NSP1 is a nuclear pore protein (nucleoporin) essential for cell growth. To identify the components that functionally interact with NSP1 in the living cell, we developed a genetic screen for mutants that are lethal in a genetic background of mutated, but not wild type NSP1. Fourteen synthetic lethal mutants were obtained, belonging to at least four different complementation groups. The genes of two complementation groups, NSP116 and NSP49, were cloned. Like the previously described nucleoporins, these genes encode proteins with many repeat sequences. NSP116 and NSP49, however, contain a new repetitive sequence motif 'GLFG', which classifies them as a subclass of nucleoporins. NSP116 and NSP49, tagged with the IgG binding domain of protein A and expressed in yeast, are located at the nuclear envelope. These data provide in vivo evidence that distinct subclasses of nucleoporins physically interact or share overlapping function in nuclear pore complexes.