Centrosome-associated RNA in surf clam oocytes

doi:10.1073/pnas.0602859103

Centrosome-associated RNA in surf clam oocytes

*Department of Cell Biology, Louisiana State University Health Sciences Center, New Orleans, LA 70112;
^§Department of Biology, Rensselear Polytechnic Institute, Troy, NY 12180;
^¶Wadsworth Center, New York State Department of Health, Albany, NY 12237; and
^†Marine Biological Laboratory, Woods Hole, MA 02543

Communicated by Lynn Margulis, University of Massachusetts, Amherst, MA, April 11, 2006 (received for review October 20, 2005)

Abstract

Centrosomes are the major microtubule-organizing center in animal cells. They are composed of a pair of [9(3) + 0] centrioles surrounded by a relatively ill-defined pericentriolar matrix, provide the ciliary centriole–kinetosome (basal body) progenitor, and organize the assembly of microtubules into the mitotic spindle during cell division. Despite >100 years of microscopic observation and their obvious significance, our understanding of centrosome composition, dynamic organization, and mechanism of action is limited when compared with that of other cellular organelles. Centrosomes duplicate only once per cell cycle to ensure development of a normal bipolar spindle. The initial event in centrosome duplication is centriole replication, which is generative, semiconservative, and independent of the nucleus. Such observations led to the proposal that centrosomes contain their own complement of nucleic acids, possibly representative of an organellar genome comparable with those described for mitochondria and chloroplasts. The consensus in the field is that centrosomes lack DNA but may contain RNA. We isolated centrosomes from oocytes of the surf clam, Spisula solidissima, and purified from them a unique set of RNAs. We show here by biochemical means and subcellular in situ hybridization that the first transcript we analyzed is intimately associated with centrosomes. Sequence analysis reveals that this centrosome-associated RNA encodes a conserved RNA-directed polymerase domain. The hypothesis that centrosomes contain an intrinsic complement of specific RNAs suggests new opportunities to address the century-old problem of centrosome function, heredity, and evolution.

Footnotes

^‡To whom correspondence should be addressed at:
Department of Cell Biology, Louisiana State University Health Sciences Center, 1901 Perdido Street, New Orleans, LA 70112.
E-mail: mallie{at}lsuhsc.edu
Author contributions: M.C.A. and M.A.A. designed research; M.C.A. and M.A.A. performed research; M.C.A., M.A.A., and R.E.P. contributed new reagents/analytic tools; M.C.A., M.A.A., and R.E.P. analyzed data; and M.C.A. wrote the paper.
Conflict of interest statement: No conflicts declared.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. DQ363378 and DQ359732 DQ359733 DQ359734 DQ359735–DQ359736).
Abbreviations:

Abbreviation:

cnRNA,

centrosomal RNA.