Although it is generally accepted that nuclear architecture is an important determinant of nuclear activity, it is not clear whether cytoplasmic events, such as transcript localization and cell polarity, are affected by this architecture. Characterization of the nuclear architecture of the single-cell alga Chlamydomonas reinhardtii revealed a polarized nucleus, with nuclear pore complexes preferentially concentrated at the posterior side of the nucleus. Nuclear asymmetry was greatly exaggerated during the upregulation of genes encoding flagellar proteins, when nuclear pore complexes (NPCs) were observed to hyperpolarize to the posterior side of the nucleus while heterochromatin polarized to the anterior side. Interestingly, prior to deflagellation, the β2-tubulin gene was preferentially located in the posterior region of the nucleus, and following deflagellation, β2-tubulin transcripts accumulated posteriorly in polysome-rich cytoplasmic regions adjacent to the highest concentration of NPCs, suggesting a connection between nuclear architecture and cytoplasmic transcript localization.
Bibliographical noteFunding Information:
This work was supported by grant AI40875 to M.A.G.-B. (supplement for training of D.A.C.-R.); grant GM54887 to R.H.S.; grant CA72836 to J.L.S.; a Josiah Macy Foundation fellowship of the Marine Biological Laboratory to M.A.G.-B.; and an Anita Zorzoli, Ph.D. Memorial Fund research award of the Marine Biological Laboratory to D.A.C.-R. M.A.G.-B. also thanks Mr. and Mrs. Arthur D. Lionberger for support. We thank Steve Braut and Jeff Levsky for help with FISH and imaging. We thank Rick Fehon, Elizabeth Harris, Charles Hauser, Mitch Bernstein, Eric Wagner, Bryan Cullen, and Javier Irazoqui for stimulating discussions and reagents. We also thank Wallace Marshall and Joel Rosenbaum for enlightening discussions.