Conditional lethal mutation nup49-1 of a nuclear pore complex component gene was constructed in Saccharomyces cerevisiae. This mutation deleted one third of the essential NUP49 gene at the carboxy-terminal, but retained 13 repeats of the highly conserved GLFG domain. The nup49-1 mutant strain was viable with a slow-growth phenotype, indicating that the C-terminal is dispensable at normal growth temperature. This strain exhibited both temperature-sensitivity at 37.deg.C and cold-sensitivity at 16.deg.C. Temperature shift experiments revealed that the arrest phenotype at 37.deg.C was random in the cell division cycle. The nup49-1 mutation was tested to be recessive and is expected to be useful for the functional analysis of nuclear pore complex proteins as well as for studies of nuclear transport systems.