Dr. Markus T. Bohnsack

Adjunct Investigator of the Cluster of Excellence Macromolecular Complexes

(together with Roman Martin, Matthias Leisegang, Fabian Mück)

Ribosome Biogenesis in Eukaryotes

Ribosome biogenesis is one of the major biosynthetic pathways, which, for eukaryotes, is best understood in Saccharomyces cerevisiae (Henras et al., 2008). Yeast ribosomes consist of 79 ribosomal proteins and four ribosomal RNAs (rRNAs). The assembly of the ribosomal subunits is a highly complex process that involves more than 200 cofactors (Figure 1).
We are studying ribosome biogenesis in eukaryotes with special focus on key players involved, such as RNA helicases. ATP-dependent RNA helicases modulate RNA-RNA and RNA-protein interactions and 19 such proteins are known to be involved in ribosome assembly (Cordin et al., 2006). All of them are designated as DEAD/H box proteins with the exception of Dob1/Mtr4, a cofactor of the exosome complex required for 3’-maturation of the 5.8S rRNA. Due to the defects observed in RNA processing and the accumulation of rRNA intermediates upon genetic depletion of the putative helicases, the proteins can be grouped into different sets acting either during the early steps in the pathway of 18S rRNA synthesis or in the biogenesis of the large ribosomal subunit. Finally, Has1 and Prp43 are involved in both the 40S and 60S biogenesis pathways.
Recent years have seen first advances in the functional analysis of the RNA helicases involved in ribosome biogenesis. Several RNA helicases are required for the release of snoRNAs from pre-ribosomes (Bohnsack et al., 2008; and references therein). Other helicases have not been found to be involved in snoRNA release, suggesting that these proteins could play different roles in the pathway. Likely functions include remodelling of pre-rRNA structure in pre-ribosomal particles, e.g. to allow access of processing factors such as nucleases and/or promote the recruitment of ribosomal proteins and other factors by unmasking their binding sites. Besides being important for the efficiency of the process by accelerating rate limiting steps, helicases might also have a central role in controlling the sequence of events during ribosome biogenesis.

Figure 1: Scheme of the ribosome biogenesis pathway in Saccharomyces cerevisiae.

You can find the links to the cited articels oun our publications site.

Dr. Markus T. Bohnsack
Cluster of Excellence Macromolecular Complexes
Institut für Molekulare Biowissenschaften
Goethe Universität Frankfurt
Max-von-Laue-Strasse 9
60438 Frankfurt
Germany

Phone: +49-69-79829283
Fax: +49-69-79829286
E-mail: Bohnsack@bio.uni-frankfurt.de

geändert am 02. Februar 2010  E-Mail: Webmasterm.fauth@bio.uni-frankfurt.de