Overview Nuclear envelope membrane bilayer structure continuous with ER contains nuclear pores controls transport between cytoplasm and nucleus more active cells have more nuclear pores small molecules freely traffic large molecules require active transport mediated by importins and exportins nuclear localization signal (NLS) provides signal for nuclear access Nuclear lamina on inner face of nuclear envelope fibrous network of proteins role attach to chromatin participate in construction and deconstruction of nucleus during cell division phosphorylation by lamin kinase in prophase results in blebbing of nuclear envelope Nucleolus location of rRNA synthesis site of ribosomal assembly