Nucleocytoplasmic mRNA transport.

Abstract

How do messenger RNA molecules (mRNAs) migrate from the nucleus to the cytoplasm? Messenger RNA precursors (pre-mRNAs) are synthesized in the nucleus by RNA polymerase II and are then subjected to a series of processing reactions which include the addition of a 7-methylguanosine cap at the 5’ end, the removal of introns by splicing, and the generation of mature 3’ ends, usually by polyadenylation. Mature mRNA molecules are then translocated to the cytoplasm through the nuclear pore complex. This process must be selective, because unprocessed pre-mRNAs are not exported. Although the detailed mechanism of mRNA nuclear export is not yet well understood, recent work has begun to lay a useful framework for understanding the nature and regulation of this fundamental biological process. This chapter will describe the essential features of mRNA export. Due to space limitations, much important and interesting work on mRNA transport in viral model systems will not be included. However, a number of good recent reviews on mRNA export have been published (Corbett and Silver 1997; Nakielny et al. 1997; Nigg 1997; Izaurralde and Adam 1998; Ohno et al. 1998; Stutz and Rosbash 1998; Adam 1999).