The current revolution in proteomics and systems biology is driven by new analytical tools
that are both fast and sensitive. Among these tools, mass spectrometry has become the
method of choice for rapidly identifying proteins and determining details of their primary
structures (1). Currently, there are two complementary lines of attack for the mass
spectrometry analysis of proteins: the bottom-up and top-down approaches. On page 109 of
this issue, Han et al.(2) extend the range of the top-down approach to proteins with …

Downloaded from interesting questions. How is the relative abundance of TFII-I in the
cytoplasm and nucleus determined? TFII-I phosphorylation causes TFII-I translocation into
the nucleus (14), and yet this phosphorylated form of the protein also binds to PLC-γ in the
cytoplasm. Understanding precisely how these two pools of TFII-I are regulated will reveal
how the two functions of the molecule are controlled. PLC-γ also plays a key role in
activating many signaling enzymes, including protein kinase C, and TFII-I may regulate …