Nucleic Acids Research Advance Access originally published online on September 12, 2008
Nucleic Acids Research 2008 36(18):5832-5844; doi:10.1093/nar/gkn549
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Nucleic Acids Research, 2008, Vol. 36, No. 18 5832-5844
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Dicistronic tRNA–5S rRNA genes in Yarrowia lipolytica: an alternative TFIIIA-independent way for expression of 5S rRNA genes
1Saclay Biology and Technologies Institute (iBiTec-S), CEA, 91191 Gif-sur-Yvette CEDEX, 2INRA UMR1238, CNRS 2585, AgroParisTech, Microbiology and Molecular Genetics, BP 01, 78850 Thiverval-Grignon and 3Architecture et Réactivité de l'ARN, Strasbourg Louis Pasteur University , CNRS, IBMC, 15 rue René Descartes, 67084 Strasbourg, France
*To whom correspondence should be addressed. Tel: +33 1 69 08 46 20; Fax: +33 1 69 08 47 12; Email: christian.marck{at}cea.fr
Received June 26, 2008. Revised August 7, 2008. Accepted August 12, 2008.
In eukaryotes, genes transcribed by RNA polymerase III (Pol III) carry their own internal promoters and as such, are transcribed as individual units. Indeed, a very few cases of dicistronic Pol III genes are yet known. In contrast to other hemiascomycetes, 5S rRNA genes of Yarrowia lipolytica are not embedded into the tandemly repeated rDNA units, but appear scattered throughout the genome. We report here an unprecedented genomic organization: 48 over the 108 copies of the 5S rRNA genes are located 3' of tRNA genes. We show that these peculiar tRNA–5S rRNA dicistronic genes are expressed in vitro and in vivo as Pol III transcriptional fusions without the need of the 5S rRNA gene-specific factor TFIIIA, the deletion of which displays a viable phenotype. We also report the existence of a novel putative non-coding Pol III RNA of unknown function about 70 nucleotide-long (RUF70), the 13 genes of which are devoid of internal Pol III promoters and located 3' of the 13 copies of the tDNA-Trp (CCA). All genes embedded in the various dicistronic genes, fused 5S rRNA genes, RUF70 genes and their leader tRNA genes appear to be efficiently transcribed and their products correctly processed in vivo.