Restricted distribution of mRNA produced from a single nucleus in hybrid myotubes.

Although the proteins encoded by a single nucleus in multinucleated myotubes have a wide range of distributions within the myofiber, little is known about the distributions of their mRNAs. We have used hybrid myotubes in which one or a few nuclei are derived from myoblasts that express nonmuscle proteins to investigate this question. We find that three different mRNAs, encoding proteins that are, respectively, nuclear, cytoplasmic, and targeted to the ER, have similar distributions within myotubes. Each is confined to an area within approximately 100 microns of the nucleus that expresses it.