Factors to consider in nuclear transport
1) Nucleus surrounded by envelop composed of two concentric membranes (out and inner).
Both evolved from plasma membrane.
2) Traffic must go in 2 directions: Histones, gene regulatory proteins, DNA and RNA polymerase, and RNA processing protein must be able to get in.
tRNAs, processed mRNA, ribosomal subunits must get out.
3) Mitosis: Nuclear envelope disassembled and must reform.