HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Summary Full Text Full Text (PDF) All Versions of this Article: fj.05-5278fjev1 20/11/1901    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cisterna, B. Articles by Biggiogera, M. Search for Related Content PubMed PubMed Citation Articles by Cisterna, B. Articles by Biggiogera, M.

Small ribosomal subunits associate with nuclear myosin and actin in transit to the nuclear pores

Barbara Cisterna^*, Daniela Necchi^*, Ennio Prosperi and Marco Biggiogera^*,,1

^* Laboratorio di Biologia Cellulare e Neurobiologia, Dipartimento di Biologia Animale, Università di Pavia, Italia; and

Istituto di Genetica Molecolare del CNR, Sezione di Istochimica e Citometria, Università di Pavia, Italia

¹Correspondence: Laboratorio di Biologia Cellulare e Neurobiologia, Dipartimento di Biologia Animale, Università di Pavia, Piazza Botta 10, Pavia 27100, Italy. E-mail: marcobig{at}unipv.it

ABSTRACT

We have followed at high resolution the ribosomal protein S6 entering the nucleus of HeLa cells, stopping in some (not all) interchromatin granules clusters and reaching, via Cajal bodies, the nucleolus. There, S6 is assembled with other proteins and rRNA into small ribosomal subunit (SSU), released in the nucleoplasm, and exported through the nuclear pores. We show for the first time the spatial association of nuclear myosin I (NMI) and actin with the SSU already at the nucleolar periphery to the nuclear pore. A blockade of NMI or actin induces an upstream accumulation of the S6 protein en route to the nucleolus, and a temperature lower than normal influences RNA export. Our data strongly suggest a functional relationship of SSU with NMI and actin. In our hypothesis, an active, myosin-driven movement of the small ribosomal subunit can be responsible for the export of 10% of SSUs. This hypothesis is supported by ultrastructural, immunofluorescence, and biochemical analyses. The currently accepted model for the subunit release suggests a diffusive, temperature-independent mechanism. However, the advantage of the double mechanism would assure that the movement of a part of the subunits could be modulated, increased, or decreased according to the needs of the cell at a specific moment in the cell cycle.—Cisterna, B., Necchi, D., Prosperi, E., Biggiogera, M. Small ribosomal subunits associate with nuclear myosin and actin in transit to the nuclear pores.